forester,
If the hinge pin is threaded, you might be able to drill and tap it for a smaller screw. Then you have three choices, you might be able to pull it out by using the smaller screw as a "jack screw" (if a solid pin), tap it for a left-hand screw (it might back itself out in the process) and turn the hinge pin out by turning the small screw in, if the hinge pin happens to have a left hand screw you can "loc-tight" the left hand screw in and turn the hinge pin out right handed. If everything fails, you can grind the small screw head off, put the cover back on and be no worse off than before. Good luck.
Mike