Once you get all the tokens and click on the application sign again, you will automatically be zoned to the traitors area. talk to the marshall and then take care of business.
Just don't forget to check the application sign again or you will never get there.
lol, I did the exact same thing. Yes, you can get back in, just click the sign again, IIRC. There should be an open doorway that'll lead you to the traitors.
I missed that the first (few) times as well. There is an open archway that leads behind one of the walls in the room with the Marshal; that's where the traitors are.