The aircraft didn't leave the departure airport, who knows what would have happend otherwise.
My friend might have been sleep deprived, I've done something similar before. The airline I, and my friend, were flying with was Ryanair and they all look the same at 6am. I queued up for a flight to Dublin rather than Stansted when the gates were right next to each other. Easily done with little sleep!
Maybe being rushed on a turn around led to the problem with my friend?