The next step before leaving the gate is the count performed by the flight attendants. That always had to be reconciled between the flight attendants and the gate agent at my airline before the flight could be ‘closed-out’. A head count would have shown a discrepancy although tracking who is on board and who isn’t is made more difficult by Southwest’s practice of not assigning seats.
My preferred solution would be to have the passenger refunded for all money he had to expend on this trip and a written apology from the gate agent for the hassle.
he must have snuck past the boarding attendants and didn’t get his ticket scanned. His fault.
I don’t think it was the gate agent’s fault. She waved him through.
The clerk who refused to honor the second portion of his ticket and refused explanation was the jerk.