Himmelsbach wrote , " I have to confess , if I were going to look for Cooper , I would head for the Washougal . " The Washougal Valley and its surroundings have been searched repeatedly by private individuals and groups in subsequent years ; to date , no discoveries directly traceable to the hijacking have been reported . Some investigators have speculated that the 1980 eruption of Mount St. Helens may have obliterated any remaining physical clues
1980 eruption of Mount St. Helens
1980 eruption of Mount St. Helens
D. B. Cooper