I've had people steal from me before. Last time that happened it was in an auditorium and I yelled out whoever took my 'cap' better give it back. After I returned my cap was below the chair where I left it. Better get more aggressive with the 'rat faced douche' he'll cough up the truth. 

Not personally, although come payday there is always somebody who claims their wages have been stolen. It's the weirdest thing, pickpockets are rife where I am yet none of the local staff seem to take any precautions. And very few of them seem to have bank accounts.

No, mainly because there is nothing in the classroom to steal, unless one wants a chair or blackboard.

In other places, no one has stolen from me because I don't give anyone a chance. I'm always aware of who is around me, where their hands are, and I posess a large degree of suspision; not just in China, but where ever I live. It's not paranoia, just survival in a big city.