I did exactly the same thing a few years ago when flying back from Miami. It was only a small ladies Swiss Army knife , which I loved it was so useful. The American security guy spotted it and asked me what it was, I answered "it's a penknife", he looked at me in absolute disbelief, his face was a picture. "A penknife, maam, you're carrying a penknife???"
Mind you, it was also soon after 9/11 and the whole world was being super security conscious.