Something resembling this may or may not have been witnessed by a buddy of mine, and it may or may not have been recently:

A full-up plane offers its last couple seats to standby passengers minutes before pushing back. A couple of other standby passengers see the desk agent who sees their itineraries, but can't get them on this flight.

With the gates closed and the plane already heading for the runway, a (non-standby) ticketed passenger saunters casually up to the gate with the coffee s/he has just purchased, expecting to board.

S/he becomes indignant and starts heaping abuse on the desk agent when told that s/he has missed the plane and they're not bringing it back.

/cut to the ticket counter