On December 12, 1985, Mike Riemer, 36, his girlfriend, Diana Robertson, 21, and their daughter, Crystal Robertson, age 2, traveled from their Tacoma home to Pierce County, planning to find a Christmas tree. Later that evening, customers at a Kmart store 30 mi (48 km) north in Spanaway found the couple's daughter, Crystal, standing outside the store entrance. When asked where her mother was, the dazed two-year-old told her grandmother that her "Mommy was in the trees."

On February 18, 1986, over two months after the couple's disappearance, the body of Diana Robertson was discovered half-buried in snow by a motorist near a logging road off of Washington State Route 7, just south of Elbe. Riemer's pickup truck was also found near Robertson's body.

On March 26, 2011, hikers discovered a partial human skull later determined to be that of Mike Riemer. It was found in an area within a mile radius of where Robertson's body had been discovered in 1986.

After recovery of the skull, Lewis County investigators stated that they believed Riemer could have been a possible victim of homicide as well, though his cause of death could not be determined.
Based on the condition of the skull, however, authorities were able to rule out a gunshot wound to the head.