Getting out of the cubicle (Or stall) can be confusing. To do so, the following things need to be done..
1. Unravel all toilet paper and grab the TP roll.
2. Grab the cellphone off the floor.
3. Open the cellphone and complete all interactions:
- Call the number on the TP roll.
- Try to open the gallery and guess a password.
- Turn on the flashlight
- Open the map.
- Open the mail app.
At this point, the lights should go out and you'll hear some creepy noises. 4 bloody lines should appear on the stall.
From here you are going to want to flush the toilet 4 times...each time you do, 1 of the 4 bloody lines will disappear, on the third flush the lights will come back online, On the last flush you might or might not receive a message on the phone, and the door should unlock, simply open the door and walk out.
Achievement unlocked.