Puddle jumper,
I would suggest that your situation is slightly different as neither you nor your management checked in passengers knowing full well before they did so that they would not be travelling to the ticketed destination.
In my opinion your efforts to make the destination before closure are to be commended but perhaps practical realities dictate that “the no grey hair” approach would be the most prudent option. Maybe your managers should review the schedule to prevent a recurrence and the associated hassles of aircraft out of position etc. There again, perhaps there is some pressing operational reason why the last flight of the day has to be to an airport with an inflexible closure time.