As Doc bears his past, Mark appears to be growing weary of the old man’s remembering…
…and Doc appears to be growing weary of Mark’s condescending attitude toward him… What, isn’t it enough that you live rent-free? Small price, Mark, that you ultimately had to marry his daughter…
The Daily Trail 
A few points here:
1. Why would they need the map to go back to the location from which they just left? Mark’s question is naive. Besides, the trail path was marked with “strange twisted rocks and pillars”, which should stand out like neon signs in the desert. (Unless they wandered into a Krazy Kat comic strip by accident.)
2. Maybe they could not find the pile of rocks because they already REMOVED the rock pile in order to get to the mine entrance. They SHOULD have been looking for a HOLE in the ground! That’s obvious, isn’t it?
3. I’m waiting for the other shoe to drop when Doc slaps a leg and starts laughing as he confesses this was all just a practical joke played on them.