Had this exact thing happen.
I forget where I was, may have been Chicago or DC... They asked for people willing to give up their seat in case the flight was full, I said sure.
Well, the flight was called and they never said anything to anyone and closed the door.
I walk up and ask what's up and they said, oh... where's your boarding pass? I said, YOU HAVE IT... you asked for volunteers and took my pass.
I was livid.
I think Vanilla kept it together pretty well. Sometimes people just need to mind their own fucking business.