Well, I didn't mean mining in that particular spot, but in the range as a whole. To be honest, it really wouldn't take one long to climb up on a high point, say the main ridge line, and take not of the topography. I'll bet one could spend a couple of months non-stop in those mountains, having never before step foot in them, and create something like the stone maps. Back in those days that's what they did. They didn't have topo maps, and GPS, etc. There were no names for landmarks like there are now, no roads, etc. I think you get my drift.
If a large group of people had done any mining in that range at all, or hid anything worthwhile of creating a map like that, they would know the region well. This does NOT mean they are frauds, but that the person who created the maps knows the region well. This could have been any modern day person, or any old time miner/map maker, etc etc.
I didn't discover anything, just found something you discovered