I was trying to think what kind of glue was used. First I’d think it was clear so it would be less likely to be noticed. But there’s the dry time thing. It needs to not cure for how long before the victim sets in it. Then it needs to cure in the short time the victim is there.
One thought is the victim spent waaaaay to long on the potty. The other is the glue was applied immediately before the victim sat down. The image of the victim banging on the door of an occupied stall and telling the occupant to hurry up, and angering the occupant comes to mind. The angered occupant applies the offending adhesive before exiting as a welcome gesture in exchange for the victim’s rudeness.
Normally if I can’t be home I prefer the woods.