Haha,
It's not so embarrassing when you're not aware of your mistake til afterwards.
On an occasion in Prague a few years back the toilets had words instead of boy/girl pics.
Down in some basement Jazz club, I couldn't even guess which door to take.
I chose one, sat down for my business (in the only cubicle, which had no lock) and tried to hurry as best I could.
About 30 seconds in, the main door opens followed by the cubicle door.

2 gorgeous Czech ladies start to piss themselves (not literally because I was on the only lady loo) and I have to escape the club pretty soon afterwards.
On the plus side, they didn't have a camera