I feel bad for you just thinking about that. I would've gotten straight ignant (more than just ignorant) over something like that. Oh man, that would just bring out the 8 year old li'l brother in me. Where it becomes a mission to either get back the seat or ruin the movie for both of us.

Personally though I could never leave my stuff at a seat to save it unless a friend was there already. But maybe that's just Chicago in me. In fact in your situation I might have been like "Bitch you stole my drink!" Before I ever thought about the seat being taken.