I agree that this is grossly out of proportion, but why wouldn't it have been possible to go back, or send someone back, to the dressing room to collect a coin?
In a semi parallel context I recall a conductor at the Proms, I think it was Parvo Berglund in his Bournemouth Symphony Orchestra days, forgetting his baton and returning off stage to collect it amid huge laughter and applause.
As a National North watcher David McNamara seems to me to be one of the best around, I hope this doesn't damage any promotion prospects.