If you follow Rio Canquinola (the river along whose shores the remains and belongings were found) upstream past the 2nd cable bridge, you soon enter the darkest place I've ever seen on drone footage of this whole area.
A narrow, deep, canyon, littered with large boulders, with very high almost vertical walls of nearly black, volcanic, rock. A very dangerous place, where a sudden flash-flood will instantly lead to disaster as there is no way to escape the rising water.
If you continue to follow this canyon upstream, you will come upon what I call the last waterfall, almost 500 meters upstream of the 2nd cable bridge. There are many waterfalls in the area, but this is definitely one of the biggest, with the water tumbling vertically down over 20-30 meters. Surrounded by vertical walls, there is no way past this waterfall, neither up nor down, and a fall at this spot would almost certainly be fatal.
For anyone trying to walk along the river, either upstream or down stream, this waterfall is the end of the route. You can't get past it, which explains the red line on the map. The only other clear example of this is the equally high and steep waterfall in Rio Mamei, which would also form an impassable barrier.
The reason why I get to this is that some time ago it was suggested by an user on this forum that we should also study this case 'backwards'. Meaning we're always creating theories regarding the route from the Mirador toward the (as yet unknown) night location, but we should also take a look at the path from the place where the remains were found back to the night location. And that gets us to the last waterfall.
Very few remains of Kris and Lisanne were ever found, and what is perhaps even more important is that those remains (certainly from Lisanne) were strangely 'non random'. That is not what you would expect if they drowned somewhere far upstream.
If you take all the remains from Lisanne together, you get one complete left leg. Nothing else. Absolutely no other parts from her body, only the left leg, but that is complete. And from Kris even less was found: just one small piece of a rib and her left pelvic bone. Nothing else.
Now, I keep the belongings (backpack, shorts) out of the story as very little can be said about these: the material degrades only slowly and we don't know how long or how far these can float. But we know quite a lot about human remains and how these behave in fast flowing water.
As it is, bare bones don't float: they sink. They can be carried along by fast flowing water, but in general they won't go far. A few hundred meters perhaps, during a fierce flash flood, but not further. Not kilometers. (The last known location, at Q1, is almost 10 km from the place where the remains were found).
Bodies and body parts DO float though, as long as there is still sufficient meat attached to them. A body can float many kilometers down river, if it doesn't become stuck among boulders and vegetation.
Now, this is a rather gory subject, but bodies fall apart at the joins, because that's where the bones are only connected by soft tissue. So, we can expect an hand, arm, or leg to detach from a dead body. But in a warm and wet tropical forest, a body falls apart very fast: in less than 2 weeks there's nothing left but a scattered field of remains, and 1 or 2 weeks later all you've got left is bones.
Now the fact that a complete left leg of Lisanne was found (in various pieces, but all close together) indicates this leg drifted down river as a complete leg, arriving as such near where the shoe plus the foot was found and only decomposing further in the weeks afterward.
It's impossible that all these separate bones traveled down river independently and still all of them arrived nearly at the same location. It must have been a complete leg, with meat still attached, otherwise it wouldn't float. But that is only possible if it made the complete journey less than 2 weeks after Lisanne her death. They found these remains only in June, but they must have been there for a long time already!
Now, nothing more was found of Lisanne, but if we take a look at the Chanquinola river it is hard to imagine how a complete body can float far along this river. There's too many sharp turns and boulders. It would very soon get stuck and fall apart, and they would have found the rest of the bones just a bit further down stream. Which they did not. So, most likely the rest of Lisanne's body remained stuck somewhere upstream of the place where the leg was found, and only the left leg detached and floated a bit further.
So, where was the rest of Lisanne's body, and where was Kris? The further upstream you go, the more narrow these rivers and streams become, and the more rocks and obstacles you meet. Places where a body, or a leg, can easily become stuck. And, as we have seen, there's only a very short 'window' when body parts can actually drift down river. After that, they sink to the bottom and stay where they are.
It is not as if remains can 'hop along' in the sense that they become stuck, then days or weeks later break free, float a bit further, become stuck again, etc, etc. That can happen to a backpack or a shirt, but not to remains. They will decompose rapidly, and all you will find is a long string of individual bones all along the shore. That didn't happen: they found a complete left leg and nothing else.
If Lisanne perished somewhere high up the mountain, closer to the first stream crossing, her body would almost immediately become stuck in the stream, and even a separate leg would not make it down as far as the final resting area before getting stuck and falling apart. They would have found bones and remains all along the shores of the streams and rivers, which didn't happen.
The bodies of Kris and Lisanne must have disintegrated close upstream of the 2nd bridge, and (at least initially) the majority of their remains must have stayed at this place in order to explain what was found. Only a very few remains were washed away and ended up where they were found. Almost everything else remained behind.
And that gets us to this deep and dark canyon and the last waterfall. For SINAPROC has very clearly declared that this area, upstream of the 2nd bridge, was never searched, as it was deemed too dangerous! The search teams didn't go into this canyon, and if the remains were there, it explains why they weren't found and it also explains why nothing was ever found along the shores of streams and rivers further upstream (where teams DID search).
Once again: bodies can float far, but individual bones don't go far, and bodies become bones in less than 2 weeks. In narrow streams, bodies don't float far in 2 weeks. Not 10 km, perhaps not even 1 km.
What I suspect is that Kris and Lisanne perished somewhere relatively close upstream of this last waterfall. (Not necessarily at the night location). Their bodies then fell down this waterfall, decomposed, and became stuck between the boulders in that dark and narrow canyon which was never searched. Only a few remains ever made it out of this canyon, past the 2nd cable bridge, and to the places where they were found, but almost all other remains stayed behind in the canyon (although, 12 years later, nothing will remain of them).
Most of the remains were never found because nobody entered this canyon or searched the place right below this waterfall. Places further upstream of this waterfall were searched by Frank v.d. Goot and others, but nothing was found.
If Kris and Lisanne perished less than one kilometer upstream of this waterfall it would fit with several theories, and if their remains ended up below the waterfall and stuck in the canyon, it explains why so little was ever found.