In labyrinthian, there is a pool of water with a skeleton and a chest in it. It has some ore as well if I remember correctly. Anyway, there is a large stone block in the corner of the pool with a ring resting on it. The skeleton appears to be reaching for the ring. I can't pick the ring up though. Is this something? Should I forget about it? I'm so intrigued!
So, I know this reply is super late, but it turns out that the ring is a Golden Diamond ring. The problem with it is that the creators must have placed it behind an invisble wall. If you're on pc, and you use the TCL command, you can grab it by clipping through the wall. Not sure of any other method though.
The hitboxes in Skyrim are atrocious. I can't say exactly what you need to do for this particular ring, as I can't remember what you are referring to, but just try and move around the pedestal, and even move your cursor around it to see if you can't find the hitbox (you would be surprised how terrible the hitboxes for coins are).
The other option is to use Unrelenting Force on it, but beware! You can lose it this way!
I would recommend a save/quicksave beforehand and if you can't find it after shouting, reload and try again.