The metal detectors, wands, etc. aren't for law-abiding concealed pistol permit holders like myself. No concealed pistol permit holder wants to risk having their permit revoked because they violated the law. I would never willingly bring my pistol into a hospital, and you can bet if I was injured while carrying and could tell the EMT's about the gun, I would.
I agree with the registered letter to the CEO idea. If nothing else, it might cause the clue phone to ring for them. Also, know where your exits are at all times. This is a basic survival tactic wherever you are--always look around for the exits whenever you enter a room. Think about where you could go for cover, if necessary.