Looks a lot like a dead bull I found a few years ago during a November cow season. It was very well scavenged. Lots of bird droppings, coyote tracks still visiting in the snow. This one looks a bit fresher, but the position of the skeleton, and location of the carcass looks like a wounded bull sought out a well worn elk bed in timber, lay down, and succumbed to its wounds. The spot looks like a bed, the elk is at the base of a relatively large tree, and the body is positioned in a place a bull would have bedded. I think after death, they all generally stretch out in rigor mortis. This does not look like a human took meat off it and left the head. As someone mentioned, it is unlikely a guy would try to bone it without first disjointing the legs. Having done a lot of boning, I can't imagine leaving it fully assembled and trying to bone it out, especially the side on the ground. At a minimum getting the legs off one side makes it much easier to turn over to work on the other side.
I took the head, but because this is WY, I took it right to a game warden and described how it was found. I got an interstate tag, and was allowed to keep it. That was I am sure in part because the warden knew me pretty well, and believed my story. It probably helped that even as old as it was it was still very gaggy. In CO, I believe you are OK to pick it up. Having your photos of how you found it, is probably a very good idea. Maybe a call to CDOW to check on procedure would be good. It is possible a warden might want to visit the site with you.
Good luck. Don't wait too long or someone else might get it.
