Fred Claassen entered the Hoover Wilderness from Twin Lakes on Thursday, July 31, 2003 for a short hiking trip to Crown Lake. He planned to traverse Mule and Burro passes and return to Twin Lakes cross-country via Matterhorn Pass and the Horse Creek drainage. Due back Monday, August 4th hikers reported seeing him last at Crown Lake on the afternoon of Friday August 1st. He has not been heard from since.