He says he found the treasure months ago, and is willing to reveal his identity now because another treasure hunter sued and seemed close to exposing his identity. Still won't say where he says he found it though, and says he might sell it off in pieces.
A decade ago, [Forrest] Fenn hid his treasure chest, containing gold and other valuables estimated to be worth at least a million dollars, somewhere in the Rocky Mountains. Not long after, he published a memoir called The Thrill of the Chase, which included a mysterious 24-line poem that, if solved, would lead searchers to the treasure. Fenn had suggested that the loot was secreted away at the place where he had envisioned lying down to die, back when he’d believed a 1988 cancer diagnosis was terminal. Since the hunt began in 2010, many thousands of searchers had gone out in pursuit—at least five of them losing their lives in the process—and the chase became an international story.
Over time, those teenage dreams of adventure receded, and [the man who says he found the treasure] went on to attend Georgetown University, where he served as editor in chief of the Georgetown Heckler, a campus humor magazine. He graduated in December 2009 and began a career as a writer, both in humor—he worked for the Onion—and in more traditional media. He became embroiled in a few controversies early in his career, both at Wonkette, ... and while freelancing for Buzzfeed
He soon entered a postbaccalaureate program, and then enrolled in medical school. But he disliked most everything about medicine beyond treating patients, he says, and something else captured his attention
Here's how the the article's author managed to contact him through Medium:
I had one trick up my sleeve, though. There’s a little-known way to send a direct message to the author of a Medium story: you flag a section of text, indicating that it contains an error or typo. This notifies the author that something needs to be corrected. The system doesn’t give you a lot of space, just enough to describe the problem. So I flagged a section, barely squeezed in who I was and my email address, and hoped for the best.