Yeah, the story doesn't really tell us much. I'm willing to bet he forgot it was there. Even the most dilusional criminal wouldn't believe that getting a gun through security would be that easy. It's one thing to forget you have one in your pocket, but far more likely to forget it is in a carry-on bag. Not that I'm excusing it, as I believe carrying a gun demands that you always keep it's presence in the back of your mind. I think they will realize that there was no intent, and go easy on him.