If I am not mistaken, this is yet another 'airline myth' fable that has been doing the airline rounds for years! Stick any story that comes through the internet into snopes.com and you will find that they invariably come up phony. This 'locked in toilet fable' (always with the least popular crew members- for cabin crew read Flight Deck- for maximum impact) has been doing the rounds in my flying career since 1970. It is told around so often that people often actually believe they were there.
Quite simply lad.......you been had! Nice story. all that's missing is an element of truth! But you will come back and say whoever told you it was actually there! Yeah yeah