First off, even full time staff had to pay to attend this convention. We just paid less because we would be putting a lot more work into this convention than most of the other attendee's. (I had 12 hour shifts, and other people did to.)
So, on occassion, we actually had time off to enjoy an event. By being on staff, we were forced to miss a lot of the Con, but would make room in our VERY busy schedule for at least one event. (I got to see Opening Ceremonies because my shift was all night, even though I was supossed to be sleeping. Me being at FanFic Bedtime was because I was actually running a high fever, and had been relieved of active duty because I could not make acurate judgement calls.)
So don't be mad if you see a staff member attending an event. Even we need a break for rest and relaxation.
About the Master Plumber Prize thing, I have no clue. Staff was not eligable for it. Are you sure it wasn't a volonteer? All I know is that the Staff wasn't even eligable for Hallway Costume awards. Volonteers were.