Today as I was walking, I suddenly noticed a pebble in my left shoe. It was a pretty small one and for a while it just kind of bounced around my shoe. First it was under the ball of my foot. Then it was bouncing around my toes. Eventually it was near my heel and I couldn't feel it for a while, then it was gone. Several miles later it was bouncing around my toes again.
Here's my question. How does someone get a pebble in her shoe? I've worn the shoes only one time before today. I've been walking on roads and paved trails. So, how did I get a pebble in a new shoe?