myroundaphobia

Noun. A phobia of buying a round in the pub. Sufferers often encounter extreme bladder problems requiring immediate trips to the bathroom when its their round. Sufferers with extreme cases have been know to vanish altogether.

Cures for extreme cases involve offering to skip their turn to buy a round, which at times results in almost magical reappearance of said sufferer.

I am not sure why he got stuck trying to climb out of the Gents' loo. Perhaps it is a case of myroundaphobia.