Had another idea after watching Urban legends.
A female college student is visiting an asylum for a report. As she goes to leave, she realizes that somewhere during her tour she dropped her visitor's pass. The orderlies, noticing she looked just like a girl they had allowed to escape earlier in the day detain her, saying she's lying and she's actually the girl who escaped.
After some thinking on this one, instead of a student, it can be someone undercover investigating the asylum. They can realize what she's doing and detain her, locking her in solitary, basically making her disappear without killing her.
Now quite sure where all to go with this one. I'm up for most ideas. PM me if interested.