It doesn't work that way. The sign itself means absolutely nothing. You must be asked to leave. Now, it is entirely possible that they could lie and say that they asked you to leave, but you refused. That's when a voice recorder comes in handy. And there are also cameras all over the place, I'm sure, which could be used to vindicate you if you actually complied and they say you didn't.
If it's concealed properly, and I'm sure Steve knows what he's doing in that regard, then they're not going to just happen upon it. If, however, they do use the wand and pat downs and metal detectors, then there might be a problem.
You think to much about chit