We have a vending machine here whereby you put your money in then slide a door open to get what you bought. it has sandwhiches and stuff in. Kinda like this...
This guy I know likes to grab you mobile phone or wallet and get some food out and put your item in the vending machine when he takes his out. Meaning you have to pay £1.70 if you want to get it back (although he pays in the end so it's an expensive prank for the guy).