I don’t buy the argument that theft isn’t as bad if people leave something out “in the open”. We all have
amazon packages sitting out on our porches and mailboxes—doesn’t make it not theft if someone steals them. We all set our belonging down on a lounger in
castaway cay to go for a swim, but if someone walked up and down the beach swiping sunglasses and beach toys off chairs that’s theft too.
It also doesn’t work to say disney has no interest in policing guest on guest misbehavior. Of course they do—they do it all the time. If a guest is smoking in a nonsmoking area or a family brings their kids into Serenity Bay or the adult pool, that does not cost Disney anything directly, but it impacts the guest experience negatively and costs them repeat business in the long run.
And yes bratty parents will whine and fuss if their kids are called out, and yes that creates awkwardness for Disney, but I see that play out every single cruise when spoiled parents argue with the staff when their babies in diapers are turned away from the family pools, or the staff has to remove shrieking popcorn throwing kids from the theaters, or kick a kid out of the kids club for bullying.
I also don’t think it is fair to call FEs junk/trinkets. True some are, but a lot of guests put a lot of time and money into thoughtful gifts. We once got a set official disney parks minnie ears (retail for $30+ each), embroidered high quality towels and beach bags, custom yeti brand mugs, jewelry and other nice quality items. I have been spending less on FE lately and doing homemade items, but that doesn’t make my gifts less valuable to me—I spent over 40 hours painting and sealing individual hand painted coasters for each guest in my group, and my FE group loved them and it meant a lot to me they were so happy. I was nervous they’d be taken so put them put early morning on the theory that teeens taking stuff were likely night owls sleeping in. We’ve gotten similar things like hand sewn or crafted items and I know it is a lot of work. There is also pin board theft that happens in addition to FE theft and pins are quite pricey—I don’t do that, but I feel bad for folks who had their entire boards cleaned out.
So yes I do think Disney should review camera footage and confront thieves (if they are minors, then their parents). Kicking off the ship seems extreme, but at least talk to the parents (I do think some would listen and be mortified and revoke their kids' free roaming privileges). They can search the culprit’s room and store stolen pins/items to the owners. They could charge the guest’s account for value of stolen items like they do for people who steal the blankets from rooms. In short, they could treat this like any other crime on the ship.