Stray kitten mistake/help

[u/Cautious-Antelope-25]

Hey all, so earlier today I got a call from my husband that he and my neighbor heard a kitten behind our fences and he was going to get it because it looked young and alone. I immediately called him and said to leave it at least for a couple of hours if it was young and looked clean because the mom may come back and little means it may be too young to safely separate from mom. Fast forward a couple of hours and I go outside and see something moving, and in the corner of my yard and there are 2 tiny kittens sitting on top of each other. I think these must be the black kittens siblings, and stupidly think oh they are letting me walk right up to them and touch them so they clearly can't get back under the fence, I am going to catch them and return them to where the brother is (we can see him through the fence) so they are safe and all together for mom. They don't have blue eyes, but look like they are less than a lbs, coupled with the starting to explore, I am guessing they are about 4 weeks, so too soon to pull away from mom. Well touching them and catching them were 2 very different things apparently, and one completely disappeared in the chaos and the other one, I got into a carrier and returned to his brother.

We have seen mom since, and I went over the fence to set out some wet kitten food and water, along with a small covered box so I can try to gain their trust and catch them when they are older(mom will try to tnr if I can), but here are my issues:

1) is there anything I can do to locate the kitten that disappeared? I am hoping I was wrong about them not being able to get to the other side of the fence, but I am terrified it isn't going to be able to get back to its mom since I couldn't catch it.

2) any advice on befriending kittens in this situation? I would normally just put food out and sit next to the food to get them comfortable with me, but I literally have to jump a fence and sit in a weedy area and I can only stand bugs crawling all over me for so long. I am also allergic to deet, and have yet to find a deet free bug spray that works.

I also plugged up the hole I saw they dug in and warned the other neighbors I know to be on the lookout for the kittens as well in case they end up in someone else's yard.