What happened to Günther Nothdurft and Franz Mayer as noted in the nonfiction book, The White Spider: The Story of the North Face of the Eiger?

After Longhi and Corti met with accidents during the 1957 climb, Nothdurft and Mayer attempted to finish the climb and disappeared. Years later, it was discovered that the two climbers made it to the summit but died on the way down the mountain. Their attempt is now considered the fourteenth successful ascent of the mountain.