Karen Lee Valdez-Blackburn was 26 and working as a vehicle mechanic with the 90th Transportation Squadron at F.E. Warren Air Force Base when she was last seen in Cheyenne, Wyoming on November 21, 1983. Witnesses reported watching her load her yellow Dodge Ram pickup truck, which carried Colorado license plate 4250JX, and she told a friend she was leaving, believed to be headed to Denver to visit another friend.

A month after she disappeared the U.S. Air Force classified her as a deserter on December 21, 1983. Decades without contact led authorities to later change her status to missing; the Air Force has since said it is unclear whether her disappearance was voluntary. She is described as a white female, blue eyes, brown hair, 5 feet 1 inch, about 115 pounds, and had family ties to Florida.

The case is considered cold and the Air Force Office of Special Investigations is still seeking new leads. If anyone knew Karen, saw her yellow Dodge Ram with plate 4250JX, or has information about her movements in November 1983, please come forward.