Mystery lingers: Discovery of trapper's skull adds clue to couple's 1985 disappearance

The partial skull was found March 26 within a mile of where Robertson's body was discovered 25 years earlier. The wooded area near Mineral had been searched several times in the late 1980s.
The partial skull was found March 26 within a mile of where Robertson's body was discovered 25 years earlier. The wooded area near Mineral had been searched several times in the late 1980s.

The mystery of what happened to a Puyallup trapper missing for more than 25 years is closer to being solved after a hiker found a partial skull in Lewis County.

But the discovery also renews questions about what happened to Michael L. Riemer Jr. and his longtime girlfriend, Diana Robertson.

Robertson’s remains were found buried in the snow along a logging road between Elbe and Mineral on Feb. 18, 1986, two months after she and Riemer failed to return home from a trapping trip.

Nothing was ever heard from Riemer.

“We don’t know what happened,” said Stacy Brown, chief deputy of the Lewis County Sheriff’s Office. “The fact that we found him lets us know he’s not out there running around, but it doesn’t necessarily change what we have to work with to figure out what happened.”

The partial skull was found March 26 within a mile of where Robertson’s body was discovered 25 years earlier. The wooded area near Mineral had been searched several times in the late 1980s.

A King County forensic pathologist used dental records to identify the remains as Riemer’s. It’s not known how long Riemer has been dead or his cause of death, Brown said.

He has been considered a person of interest in Robertson’s slaying because he remained missing after she was found. More than two decades ago, however, friends and family members worried that he, too, was a victim of foul play.

Pat Lemagie, who retired from Pierce County Sheriff’s Department in 2001, had been involved in the search for the couple and remembers speculation that Riemer might have been involved Robertson’s death.

“I thought they were both dead,” Lemagie said Tuesday. “And that’s what it has turned out to be.”

A Pierce County sheriff’s detective is reviewing the case and will work with Lewis County investigators to try to solve the mystery.

“We have our detective looking at it now,” Pierce County sheriff’s spokesman Ed Troyer said.


Riemer, a 36-year-old Puyallup resident, was last seen alive Dec. 12, 1985, as he left with Robertson, 21, and their 2-year-old daughter, Crystal, to check his animal traps along the Nisqually River near Elbe, according to News Tribune stories.

Riemer had worked as a roofer and boosted his income in the winter by trapping minks, coyotes, muskrats and bobcats, then selling their furs. He checked his traps along the Nisqually River at least every other day, a friend told The News Tribune in 1985.

The couple never returned from the outing.

The couple’s daughter mysteriously appeared later that day. Dazed but otherwise unhurt, the child was found wandering around by herself at a Spanaway Kmart store.

At first, no one knew who the little girl was or where her parents were. She was placed in a foster home.

A couple of days later, her foster mother took her to Mary Bridge Children’s Medical Center for treatment of minor scratches on her arms and a few bruises. A nurse recognized her as Crystal after seeing the missing girl’s photo on the news.

When Robertson’s mother, Louise Conrad, went to identify the girl, the toddler ran up to her and cried, “Grandma!”

At the time, Conrad described the usually lively girl as not happy and staring blankly when someone asked where her mother was. She told The News Tribune she sensed her granddaughter had seen something or knew something.

“She’s always looking around,” Conrad said at the time. “She’s withdrawn. Her personality definitely isn’t the same.”


Riemer’s father, Michael “Lloyd” Riemer Sr., put up a reward to find his only child. The retired state game warden also led several searches of areas where the younger Riemer liked to set up traps. Friends went up in airplanes in their quest.

The efforts were futile.

More than two months later, a Puyallup resident walking his dog near a logging road off state Route 7 between Elbe and Mineral found Riemer’s red Plymouth pickup, then Robertson’s partially decomposed body nearby.

She’d been stabbed multiple times, and a tube sock had been tied around her neck, according to “Unsolved Mysteries,” which aired a segment on the case in 1989.

Investigators found a note that read, “I Love You, Diana,” written on a large manila envelope placed on the truck’s windshield, according to News Tribune stories from 1986. Blood was found on the passenger seat, but forensic tests could tell detectives only that it was human, a Lewis County sheriff’s detective told “Unsolved Mysteries.”

After the discovery, search and rescue crews conducted several missions to try to find Riemer. They looked in the same area where his skull recently was found, Brown said.

“It’s very wooded, very thick underbrush,” she said.

After the case was featured on “Unsolved Mysteries” several tips came in about Riemer’s whereabouts, but again, they led nowhere.


At the time of the couple’s disappearance, investigators had at least two theories.

They were looking into whether Reimer killed Robertson. There had been a history of violence in the relationship, and Robertson had recently received a court order prohibiting Riemer from contacting her.

According to a 1986 story in the Seattle Post-Intelligencer, he was arrested and cited for domestic assault after Robertson told police he kicked in a door at her apartment, threw her to the floor and rubbed her face in the carpet.

“Riemer was a person of interest in the death of Robertson as he had not been located after Robertson’s body was found and his whereabouts were still unknown,” the Sheriff’s Office said Tuesday.

Detectives also wondered whether their disappearance could be connected to the slayings of a Tacoma-area couple found four months before, according to “Unsolved Mysteries.”

Ruth Cooper and Stephen Harkins were found dead in 1985 in a wooded area of Pierce County, about 15 miles from where Robertson’s remains were found.

Harkins was discovered first. He’d been shot in the head in his sleeping bag.

Cooper’s body was found two months later in heavy brush. She had a sock tied around her neck much like Robertson, a sheriff’s detective told “Unsolved Mysteries.”


The Robertson-Riemer case eventually went cold. Detectives retired. Riemer’s father died in 1993.

Now, the case has new energy with Riemer’s skull being found. Detectives and Search and Rescue personnel already have combed the wooded area where the skull was located, looking for more evidence.

The Pierce County Sheriff’s Department’s cold-case detective is reviewing the case and looking to see whether there are similarities between it and other solved – or unsolved – slayings.