Can't happen, as you know you must push the interlock button to shift out of park. Your year may even have the brake pedal interlock, In any event even without the interlocks it would not happen unless it was a high speed wallop that accordianed your car, transmission and shifter linkage in which case you would not even have a car.

I suppose if your shift linkage was grossly worn or out of adjustment it is possible to think it is in park according to the shift indicator when actually the tranny is R. Your car would then roll away on any incline if brake parking was not set. I think you would be aware of this problem in daily driving as the other positions on the gear selector would not line up properly.
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David Hunter