Back in the mid 80's, back in my youth was a mainframe operator for a company in London. 2 shifts - morning and evening, with evening shift locking up the building once everything was finished for the day.
There were 2 doors at the entrance to the building - with just enough between them that both doors couldn't be open at the same time. The inner doors were on magnetic locks, which could only be opened by pressing a button on the inside if you didn't have the right keys.
I was the evening shift... Finished the job, put the mag tapes in the firesafe (those were the days..), had a quick scoot around the building (4 floors) to make sure there was no-one about and went home, locking the doors behind me.
The following day, I had a call to my manager's office to be asked if I'd checked the building before going. I had (honest guv) - but why?
One of the developers had been working late - and on hearing me putting the mag tapes away he'd decided to put on his cycling gear and go home; he'd switched off his terminal (ahh 3270!), switched off the lights and headed to the gents to get changed.
I did my rounds, saw no-one, no lights and naturally assumed the place was empty (I have to point out that we always checked the toilets too just in case, but on this occasion the dev concerned went to some toilets I'd already checked) .
Outcome was, he got stuck in the 5 foot "lobby" between the 2 doors, unable to open either one. Eventually he managed to attract the attention of a passer-by by shouting through the letterbox, who in turn called the police and they in turn called my manager (as registered key holder) to rescue him...
If he worked late after that, he always made sure he was visible to the ops!