Car rolled backwards after hit in park.
 

Hi I have a 98 Cadillac STS with about 150,000 miles. It was parked in a parking lot the other day and while I was in the store, a lady tried to park in the spot in front of my car, but went too far and hit it head on. My car was in park, but it rolled backwards about 10-15 feet after it was hit. It drove home ok, and I didn't notice the transmission slipping or anything, but I'm wondering how it could roll backwards if it was in park. Is this some type of safety feature on the transmission to prevent damage? Any help or opinions would be greatly appreciated.

A trans is designed to roll out of park on it's own isn't really what I would call a safety feature!
How hard did it get hit?
It's possible that shift linkage, or cable, is loose. A sudden jar could have allowed the park pawl to move enough to allow some movement of the vehicle. The park system on the 4T80E trans is pretty hefty..not likely something broke...more likely it just got jostled enough to allow the movement. I would suggest having the cable, and external linkage checked. I would also suggest using the "Parking" brake....;)

I would certainly check the shift linkage because I had a late model Camaro that had about 120k and do to continuous shifting it became looser and would even pop out of drive while driving. Scary stuff and I hope you get it remedied before you park on a steep grade.

Just send the bill to the parking lot plower also :)