Sorry to hear the owners arent helping. Im no rangler or Old Dog. Your last picture appears to me to be a site of interest. Being close to water would be a bad place to put a hole in the ground. So you may wish to search the area of the large tree to the right up on the bank. In the case they did bury something in the creek, you would need to find a place of disturbance. The more junky the better. I follow the KGC post at times to see how they search, and since I dont have trees(much) here, I cant help.
It could be the area is a starting point for what appears to me as three trails. You would have to follow them out. I always carry a few bottle caps and such when Im out hunting, in case anyone ask. No one has ever told me to leave if they think Im looking for expent brass casings.
When you climb the big tree. Look for symbols in the tree itself up there. Also look as far as your eyes will let you. See if anything doesnt pop out at you. If not, just take pictures. I always do a panorama to make sure the trail didnt double back on me.
Good luck with the hunt. Really check out that big tree, especially around the roots.