RCA777: I made the trek up to the first stage of the cache... and I found it indeed to be missing the large diamond. I had a "spare" with me.... but that wasn't going to be useful. The first container contained the information sheet and the box for the diamond. The diamond... and the combination lock contraption... were gone.
Well, the lock was expensive... but I thought I'd check the final cache in case someone had mistakenly relocated the items to the final. Well.. the final ammo can was gone also. Wow. That's a long hike to scoop an ammo can and a lock.
Thanks to all who visited; this was one of my favourite hides to date.