A stuck-down shock will eject its air can at a hell of a rate, I'd be taking a few more precautions.
First thing to try is to pump it up really hard to see if you can blow it open again - Fox recommends 250psi. Then let all the air out, whether that works or not. Cycle the shock, release air again. Do that a few times - there's a good chance that some of the air the wrong side of the seal will creep back through as you cycle it so you may be able to get most of it out. Then take the can off. The usual method is a bar through the shock eye, but that's likely to hurt if it blows off. Best tip I've seen is to use one of those plastic strap oil filter wrenches with the other end of the shock in a vice and a cardboard box over the hole thing -- cut a slot in the side for the wrench handle. Can't go far then