Obviously you hadn't a misspent youth?
You may know someone that had?
You may live in an undesirable part of town, if so just ask your next door
neighbour?
If non of the above apply, you could consider breaking the smallest
window that will allow excess to a door lock/handle on the inside.
Some of the other members may have better ideas.
Oh, a coat hanger may fit between the door and pillar to work the inside
door catch, not easy but can be done (years of experience)!