getting at Plymouth Voyager spare tire...help!

I'm trying to change a friend's tire on a Plymouth Voyager. The spare is underneath the vehicle in back. There seems to be a bolt of some sort holding it in, with not much of a 'lip' to be able to grab on and turn it with. I've been doing this for at least half an hour collectively, and it has come loose, but it's very very difficult to say the least, and now it's at the point where if I turn it and then let go/loose my grip again, it just sort of spins back to where it was, like it can't go any further. Someone suggested that it unhooked from the top, such as underneath the carpet in the rear of the van behind the seat, but there is nothing there to get to. Am I missing something? Is there a trick to it I just don't understand? I think the bolt/screw is so stripped now and I've cut myself and made my arm so sore that there is nothing more I can do unless there is another way. There is no manual in the car, not that I thought a manual would be needed to get at a spare tire- when did they start making it so difficult? Any suggestions?