I had the exact same thing happen to me a couple years ago flying to Miami. I had a little cast pewter belt buckle in the shape of a 1911. I took my belt off and put it in my bag to go through the X-ray machine. The girl watching the X-ray machine FLIPPED OUT- hit the button that turned on the flashing red lights, which brought all kinds of cops running. They literally drew down on me with their pistols while the TSA guy went through my bag and pulled out my belt. With a small, flat, solid piece of pewter shaped roughly like a pistol on it. Not even a retarded monkey would have mistaken that thing for a real gun. They made a huge deal about it, threatened to arrest me, and confiscated my belt buckle- because it "resembled a gun". I spent the rest of the trip holding my pants up with a length of rope tied around my waist.
It really sucked, because that belt buckle was awesome, and I've never seen another one like it.