Actually.... yes, it has happened to me. In my case, I was showering in the basement bathroom and my family was all upstairs on the patio BBQing. The doorknob's lock jammed on me and I could not get out. Not to mention, I did not have a cellphone with me to call someone upstairs for help. I was in there for nearly an hour. I even resorted to screaming up through the vents in hopes that someone in the house would hear it echoing and come let me out.

I honestly can't remember how I eventually got out. Maybe I ended up getting the doorknob off, or it eventually unjammed, because I know no one came looking for me.