How fast were you going? I try to get my backend out on some sharp turns around my house just to get a better feel for the car and it takes alot of effort. When it does happen it is generally very controlled and easy to get back in line. You must have been cruising to have it get that far out on you.
Hopefully the damage is minimal, sounds like all seems well.
I bet your heart was pumping after you came to a stop.
