I don't understand what the legal confusion about "artful concealment" is about. To me, it's simple: it goes to intent. I think everybody here agrees that it's a crime (i.e., USC, not CFR, though I'm not going to look up the number) to attempt to bring a weapon on an aircraft. But you can't commit a crime by accident. If a TSO finds a knife in my bag, I haven't comitted a crime unless it can be proven that I meant to bring it onto the plane and you can't do that because forgetting it was in my bag is at least as likely. But if I "artfully conceal" the knife, I can't claim it was inadvertent and therefore I have committed a crime and it seems appropriate to summon an LEO.