Probably a dragging caliper or bad wheel bearing. Parking brake shoes can come apart, too, since no one ever wears them out! Or just crud piling up in there. The rotor must come off to see.
I use the parking brake all the time. Any time I'm parked on a steep incline, I set the parking brake, just to make it easier to shift in and out of Park. Set the parking brake in the manual tranny car I drive for work every time I park it.
Not terribly unlikely that the tranny will pop out of Park if someone "nudges" the car while parking in front or behind.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!