Today, as my job as a janitor....

I don't think it's that odd, there are several reasonable explanations...
Women with young male kid went to the bathroom and he wanted to pee too.
Guy was confused and went in ladies bathroom.
Pervert went in pretending to be confused.
Male's bathroom was closed or something and he had to go into the ladies restroom.
Can't think of more...

Someone had to throw up and didnt want to get the seat dirty?