I have seen coyotes eat nearly a whole deer overnight, all the way to the bone. It looked like someone had cut the meat off. I do not know how quickly a bear, wolf, coyotes and birds could eat a full grown elk, but I would bet not long.
I found a bull elk a lot more decomposed than the one you found and I took a bunch of pictures then cut the antlers off. Figured if I was stopped with them I could show pictures.
You could contact the local game officer and show him the pictures and get the okay to go get the antlers. I wouldn't leave them there for long.
