As he retraced his steps, Jon saw a flash of light about a quarter mile up the road, then he felt a light breeze blow past him. It wasn't windy that day, so it must have been from the wishing stone.
Someone was using it! (By the way, since Jon didn't hear the wish made, he thought that this new reality, whatever it was, was normal.)
He ran as quickly as he could to where he saw the bright flash of light. When he got there he was surprised to see who was holding the stone. It was ...