There are a few books dedicated to "lost treasure" around the Colorado mountains. I bought this one at a used book store a few months ago, and it's a fun read: https://www.amazon.com/Treasure-Tales-Rockies-Perry-Eberhart...
Many of the stories are dubious, but quite a few are legit and still "lost". Lots of stories along the lines of a prospector finding a rich gold vein, or very promising claim, and then hiding it for the winter, but never get back to it for whatever reason. There are also quite a few where travelers hide a "treasure" to protect it from Indians or bandits, but can never find it again.
Many times the locations are known down to a particular gulch, valley, or mountain, and still nobody's been able to find it for 100+ years.
I think knowing the history of an area makes hiking there more enjoyable, and it's fun to peek around for treasure, but the people taking it super seriously are wasting their time, IMO. Probably cheaper and better odds to play the lottery.
Get dozens of book recommendations delivered straight to your inbox every Thursday.