How do you accidentally run 3 extra miles?

I set out today to run 7 miles near my parents' house in Cleveland. I had mostly in mind what street I'd turn around on to make the proper distance. Except by the time I got there I sorta forgot which one. So I guessed at it, and found myself pretty badly lost :(. This resulted in running 10 miles instead of 7. Oops!!! But now at least I'm pretty confident in my ability to run the 15k I'm signed up for at the end of March!!