It was door #2.....she's with a strange adult man.
She called her ex-boyfriend (the one she ran with in September). He seems like a decent kid and he called the Residential Treatment Center (RTC) to let them know where she was on the condition that they never tell her that he narc'ed her out. Deal!
The Residential Treatment Center (RTC) sent the police to the house and the guy denied having seen her, refused to let the police look inside and was generally hostile. But, without more proof, the police couldn't do anything. They did reassure Residential Treatment Center (RTC) staff that this was their first time out to that house and best they could tell, there were no felons/etc living there. Residential Treatment Center (RTC) is going to send staff there tomorrow morning and try and sweet talk her out.