As with the rest of you, I agree this is an unsual questiuon to have asked of you by a store clerk. The fact that it is so unusual would have put me on alert. Had I been asked that question, I would have immediately went into a higher state of alertness than in which I normally would be while shopping in a furniture store. I am pretty sure I would have reacted, then acted, differently than the thread starter.
I would have been wondering: Is the store being robbed? Is the guy asking me this trying to let me know something bad is happening because he thinks I am a cop? Is the guy asking me about to try to rob me? Or is he just a curious person who asks strange questions?
I probably would have been scanning this guy for weapons, and for idiosyncrasies that might give away intent, scanning the rest of the store for unusual activity or lack of activity, readying to take other action as I might find appropriate. Such further appropriate action, dependent on my assessment of the situation could be: succinctly indicate to my wife to move aside toward cover or to get out of the store, readying to take cover myself, readying to draw; knocking the so called clerk on his other end.Of course that wouold be if there was a threat sufficient to warrant such.
Otherwise I might just ask this guy why on earth he would ask me such a question and why on earth I should feel compelled to answer. If he contnued in any way about asking me if I had a gun, I might ask him if he saw a bulge in my pants would he then ask me if it was a gun too? Something to throw him off a bit, and to get us off of the subject of guns and back to why I came into a furniture store in the first place - to buy furniture not to answer nosy questions.