It happens sometimes when I park in the driveway. Despite the chocks, the slope ends up putting too much pressure on the ball. If it doesn't disengage just by raising the trailer, I'll pull the truck forward 1" and then it usually drops right out.
Gotten to the point I'm now in the habit of chocking, pulling forward that 1", then turning the truck off while I work around the hitch disengaging the WD bars, uncoupling, etc...
There's no use crying over spilled milk, unless it's on your keyboard.