Solving the Riddle
The primary source of information regarding the case is a vague 24-line poem that was written into his self-published autobiography called "The Thrill of the Chase." You can find his memoir on e-bay, in book stores, and for free online as a PDF. However, if you're looking for the poem, all you have to do is go to his Instagram account: @forrest.fenn (it's not HIS account per se, but it is representative of his ethics and personality).