Originally Posted by
UAzip
OP mentioned that the kit fell on takeoff and that as soon as the chime sounded, they jumped up to take it. What is the FA or OP supposed to do, unsafely and illegally get up while the plane is taking off to retrieve it? If you know whose it was and you take it and don't give it to the person you know is the owner, especially when it fell on the floor and slid on takeoff so the owner couldn't easily get it or ask a FA to help because it wouldn't be safe for them either, then you are stealing it or as good as stealing it by taking it. What the value of the kit is or whether it was a complimentary kit is immaterial. And it wasn't abandoned according to the OP; it fell and they had no chance of retrieving it before someone else took it knowing full well it wasn't theirs. (Not a comment on you in particular, but on the ethics of taking an item that you know is someone else's when you could return it.)
There are two different scenarios being discussed here. The original one is what you are talking about, where somebody deliberately took OP's amenity kit and made a beeline to hide it in her bag. I am talking about a perfectly innocent passenger who finds a confounded amenity kit on the floor by their seat. Of course if you saw who dropped it, you should return it. If you see somebody looking around for it, by all means volunteer it. But if nobody bothers to look for it, it is abandoned. If you want it, keep it. It is only an amenity kit, entirely fungible, no great loss to OP or the airline. OP will be given another one if he asks. The value does matter, how much effort you put in to returning something. You certainly should go to greater effort to return something valuable, either monetary or sentimental value. Why? Because you know it is something that matters to the person who lost it.