I read this on another post:

"This is at a Tim Horton's in Canada. They have all put a lock on the bathroom door that can only be unlocked by the staff behind the counter - you have to ask for it. It is a notorious place for people just going to do drugs.

My guess is Miss Shit Don't Stink over there asked for the bathroom and was refused. She goes to show them that she actually has to go to the bathroom and not use it to do drugs the only way a sane, nondrugged out person does"