A regular Frontier Airlines commuter between Philadelphia and Jacksonville, Florida where she keeps a second home, arrived at the correct gate – but then went to the restroom since the gate agent confirmed she had time.
When she returned “she found the flight almost fully boarded and the jetway door about to close” so everyone was in a rush. Frontier was apparently more interested in policing the size of her carry-on bag than in making sure her boarding pass was for the correct flight. Her flight had had a gate change.