Hi Tank,
My Uncle found the site that I think you are reffering to back in the 50's. It was about 1/2 way up Telegraph pass on the south side of the road. He retrived a large caliber machine gun from it maybe a 50 cal. not sure. He started bringing it down the mountain and it got to be to heavy for him. He said that he laid it down and got he's bearings and headed back into town for help. Mind you in the 50's Telegraph pass was a long ways from Yuma. He found help and headed back and was unable to ever find the weapon.
I have heard of many stories of repeating rifles in crates that were found and when gone back to retrive them the person could not find the same spot again.
I am a native of Yuma maybe we could get together some time and swap lies, good luck in your endevours. Hal