Locked Up is when you run upstairs to talk to your parents and the door is locked. That would be considered Locked Out, but in Locked Up, its when the door is locked because your parents are having intercourse. Of course you would not know this unless you could hear the sex noises. Hopfully you can not.
I ran up to my parents room, it was locked. I then put my ear to the door, thats when i noticed i was locked up.