SF, that is the worst feeling isn't it?
When Little Mr. April was about three years old, we were at the ocean and I was wearing my SKATEBOARDING IS NOT A CRIME tee shirt as a cover up. I would have been perhaps 35. A surfer-dude-type of about 19 approached me and asked, "Do you skate?" I said no, I did not, but that I didn't like all the hassling of skateboarders.
He said, "Wow, I was going to be so impressed!"
At first I thought he meant "look how cool you are." It took me a moment to realize that the unspoken part of that sentence was "...because you're approximately 400 years old and obviously here with your grandson."