Oh, many issues that started with TSA or baggage handlers. But no guessing about it. No yellow tag, no way for ME to get the bag. So yeah, that IS the problem.
And bigger lesson learned, never, ever, ever get rid of claim checks till you have your bags in your possession
This is the only way you can prove to anyone, airline, Disney, TSA, whoever, that you checked that bag. I mean, how else are they supposed to know? You have to realize that yes, you know your son, you realize he wouldn't lie but no one else does. And people DO lie all the time. Has nothing to do with his age either. Be they 22 or 62, they lie about missing bags.
So even you don't let Disney get your bags, if you don't keep the claim check, the airline is going to be difficult to work with too.