This always happens. Immediately before some punk ass kid moves out he steals at the very least 2 objects of value from his friends or colleagues. I remember clearly one of my friends had six of his Snes games stolen from him (including Yoshi's loving island and Super Metroid) by one of his friends that moved out to god knows where. Then one of my other friends was planning to move out and I started making a list of all my valuables and checking them everyday, also avoiding inviting him over for anything. He managed to steal another guys stuff before he moved.
I'm telling ya it's some kind of epidemic mindset to just steal stuff before moving. I've had the urge once before I myself moved, but it just wasn't cool so I refrained. The fact that friends become total richards when they learn you're about to move doesn't help either.