If someone steals an iphone from gamestop can they sell it at a different gamestop?

Ok so I'm not asking for me omg ;-; but there's a guy that's stolen three iPhones from three different gamestops and we're supposed to be on the lookout for him. I was just wondering if he brought one of the iPhones in to sell it is there a way we would know it was one of the stolen ones? Like the guy took them from the front before we even had a chance to inventory them. I don't know how if there's a serial number gamestop tracks them on or what?

Phones have serial #'s on them
once he tries to sell one back they will hold that person until the police arrives
they could try to sell it
but if on video they could end up on Americas Stupidest