One time, I locked myself outside of my own bathroom -_- a lot of the doors in my house have those doorknobs that have locks on them, but no keyholes on the other side.. and this was when I was younger (and a tad more curious about how stuff worked), but I had the doorknob locked, and the door wide open. When I closed the door, it was locked. On those doorknobs from the outside is a little hole. Luckily though I found out that with a small screwdriver, I could insert it into the hole, and turn it, causing the door to unlock.