Alright, so this happened two summers ago. My boyfriend and I had been together a few months and neither of us was particularly experienced, but we'd started messing around. We were hanging out in this park just outside of town, and since it's not used very often and we'd been totally alone for like an hour since we'd gotten there, we decided to go into the bathroom (a one room, one toilet little brick building) and have a little fun. My shirt and bra were on the floor and I was on my knees when there was a knock on the door. Since I'm not the sort of person who usually does this sort of thing in public, I freaked out and got dressed so quickly I scratched myself. It turns out an elderly couple had walked along the path behind the park and were sitting on the bench while they waited for the bathroom. The bench was far enough to the side that when the door opened, they couldn't see who was coming out. My boyfriend had to open the door and I had to slip out and move quickly with my back pressed to the wall around the corner, with the door concealing me so they wouldn't know there had been two people in there. It's funny now, but I stayed hidden behind that wall until they left, I was so embarrassed.