This is news to me but thanks for providing me with the link. Although the story of Everett Ruess is remarkable in it's amazing similarity to that of The Outrider's there are some very distinct differences.
Ruess vanished in 1934 into the Utah wilderness and "Walk In Beauty" takes place in 1866 in what was then the Arizona Territory. However, The Navajo Nation does include both northeast Arizona and southeastern Utah as well as the southwest corner of Colorado and northwestern New Mexico. So, it is entirely possible that Ruess may have met up with the octogenarian Outrider and that they swapped stories around a campfire. The Outrider may have even saw fit to give the artist a well worn pair of moccasins.