After a pushback I saw the operator of the pusback truck standing next to his truck and showing the pilots a "thumbs up" with his right hand. In his left hand he was holding something up. It looked like a key or some kind of cotter.
I could imagine that it is some kind of part that he could only have if he really is clear from the plane and didn't forget to disconnect something.
Am I right? Is this some standard procedure? If so, what was he holding?