It's on the roof. It isn't very noticeable, but it must be from a ball or something. Grr. I just saw it today. Oddly enough, my previous car had a roof dent as well - that one was from a golf ball (I used to live next to a golf course).
That's too bad. I don't live "next" to a golf course, but I live close enough that I often find myself driving by... And it is frightening how often a golf ball has gone sailing from off the course and bounced either directly infront of me...or behind me. I'm just waiting for the day I hear a clunk...