Maybe it was a bad idea to try out this short cut you saw on the map. It seems the information was outdated and the building wasn't a shopping mall anymore. As a result you couldn't just walk through the building and gaining time this way. You could enter, because someone left the door open. However, getting out is not that easy. The door closed behind you and won't move, it's stuck. The exit door needs some kind of code. Maybe, you can try and figure it out. Or maybe cause a power shortage and leave while it lasts. Good luck!
January 12, 2016