It's tricky to find, but it is located in a pile of rubble in the parking lot of the first level. If you are standing in front of the crate with the evidence on it facing the room you crawled out of it can be found by walking to the right toward the rubble in front of you.
As of 4/28/14 my Borderlands 2 trading post is officially closed. I am no longer boosting, trading, farming, etc on the Xbox360. I am entirely on the Xbox One now. If you want to play Xbox One with me, send a friend request with a message
to GT zI Drucifer Iz (those are capital I's).