I work for a company that occasionally uses a different venue, this happened on Thursday.
Before my shift started I popped to the loo. Both cubicles were engaged, so I opened the door opposite, labelled 'Rest Room'. There was a toilet along with a shower & armchair! So I locked the door and sat on toilet.
A few seconds later the door opened!! Door is a fair distance from toilet, so impossible to push door shut again while still sitting. I half stood up in a panic, heard a hurried 'Oh so sorry' and door shut again.
I very quickly finished and hurried out, cringing, there was nobody there. Now the thing is, all I saw in those few seconds was a flash of our uniform, hard to recognise the voice so I'm clueless as to who saw me, trousers down, loo roll in hand!
I'm really hoping it was one of the temporary staff who I don't really know, and see a few times a year at most, rather than one of our regular 8 staff I work with 2 days a week. I'll never know, so need to put it out of my mind.
I've since found out that the door I locked is only a 'pretend' lock, so children & the elderly think they're locking it, but can be opened from outside to prevent the danger of locking themselves in. I won't be using THAT one again!!