As far as southeast Idaho robberies go, there is another "Robbers Roost" nearer Blackfoot.....it's actually at the base of the Big Southern Butte. There was a stage holdup on what was called at the time "Root Hog Divide". The story is that the lone robber was tracked from RR into the Little Lost Valley where he was arrested. They brought him back near the site of the robbery, where he told them he would show them the cave where he put the gold. They allowed him to go into the cave, where he disappeared. When they went in the cave, they found it exited about 100 yards away. They never saw the robber, or gold, again. Twenty years later a guy showed up in the area with a map to the gold. He said the robber had given it to him as he was dying in prison in Arizona. The guy spent the summer in the RR area, but as far as anyone knows, the gold was never found.
I spent a couple of weeks working on this loot. I was finally able to determine the location of the old stage stop at Root Hog. The property is now owned by Bingham County. It's near the railroad tracks east of Atomic City. In the old days, water had to be hauled there from Webb Springs on the Big Butte. In my search, I assumed that Root Hog Divide was the high ridge west of Root Hog. I spent a lot of time detecting the trail near that ridge. But I finally decided it was a lousy place to stop the stage. Nowhere to hide a horse where it couldn't be seen from a distance by the shotgun guard atop the stage.
I finally decided the "divide" was probably what they called the narrow stretch of rough basalt lava where the railroad tracks cross the road east of the Big Butte. I was never able to find a cave as long as the one mentioned in the story. There are many caves in that general area, so it would require lots of looking to find the right one, assuming it actually exists. The only really large, long caves I know of are farther south closer to Bear Trap Cave on the Minidoka road. That treasure was approximately two gold bars weighing about 200lbs.....about 3.5 million today.
Jim