She disappeared with her passport and left behind everything else. Now, key clues point to murder

A 22-year-old Oregon woman never returned from an ill-fated sales call in 1993. Now, more than 20 years later, her mysterious disappearance still remains unsolved.

Katheryne 'Katie' Eggleston inexplicably vanished on August 2, 1993, after her first day 'out in the field' selling long-distance services by herself for her new job. 

Decades later, her case was thrust back into the spotlight after key clues pointed to murder - including a killing that shared eerie similarities to Eggleston's vanishing.

The then-recent graduate of Oregon State University, had just begun a job working for Allnet Communications - a telecommunications company based in Lake Oswego - when she was placed on various sales appointments throughout the day.

Following a morning sales meeting, Eggleston went to lunch at a Burger King near the Lloyd Center - 10 miles from her job - where employees recall seeing her, KOIN6 reported. 

Eggleston, dressed in a dark purple blazer, white blouse, black skirt and white stockings, then stopped at a sales appointment at the former Port of Portland building, just three blocks away. 

A patron inside the building reported seeing the 22-year-old woman exiting the elevator alongside a 'young man in a blue blazer'.

Five witnesses at the building stated she looked 'worried and preoccupied,' the CharleyProject.org reported. 

The 'young man' - who may have been the last person to see her - was described as having dark hair and a dark complexion, yet he has never been identified.

Shortly before 5 pm, a witness noticed a silver-gray Volkswagen Golf similar to Eggleston's parked in the Port of Portland parking lot, according to the CharleyProject.

However, Eggleston's supervisor was scheduled to meet her at 5 pm in Lake Oswego, but she never arrived for the meeting. 

Later that evening, after the new-hire failed to return to her Gresham home, which she shared with her sister, Eggleston's family and friends began to worry. 

Eggleston's disappearance was then immediately reported to Portland Police, prompting a vast and panicked search compiled of friends, family, neighbors, police, helicopters and K9s. 

Around midnight, on August 3, a security guard discovered Eggleston's vintage Volkswagen in the parking lot of an industrial complex in the 12000 block of northeast Airport Way, nine miles from her last known location.

The vehicle was unlocked, its windows were rolled down and the keys were in the ignition.

Eggleston's purse and its contents were in the front seat and her workout clothes were in the back seat, but strangely her passport was missing. 

While there were no indications that a struggle had taken place, Eggleston's family believed something sinister happened.

Investigators hatched various theories regarding her disappearance, initially suspecting the young woman fled on her own accord to evade testifying against her sister, who was battling a tax evasion case.

Taking into consideration Eggleston's missing passport and her car found parked at the airport, the theory made sense at first.

However, it was later discovered that her sister had already accepted a deal and there would be no need for anyone to testify. 

Another theory pointed to Eggleston's boyfriend, but police later confirmed his alibi placing him out of town at the time of her vanishing.

For several years police maintained their theory that Eggleston left town on her own accord, that was until another young woman, similar in description to Eggleston, mysteriously disappeared from nearby Corvallis in 2004.

Nineteen-year-old Brooke Wilberger was last seen cleaning light posts at Oregon State University on May 24, 2004. 

Wilberger's family insisted that the young girl was not the type to 'disappear on her own,' prompting a widespread search for the missing teen, ABC News reported in 2009.

Five years passed without any trace of the 19-year-old college student, leading local investigators to reconsider the circumstances between Eggleston's 1993 disappearance.

However, in 2009, as part of a plea deal, then 43-year-old Joel Patrick Courtney admitted to the kidnapping, rape and murder Brooke Wilberger and led authorities to the her shallow grave deep in the Oregon woods. 

Investigators then began to probe Courtney - who had a long history of criminal offenses, substance abuse and possible mental illness - as a possible suspect in Eggleston's case.

Authorities believe Courtney has harmed other women besides Wilberger, and Eggleston is considered a possible victim.

Eggleston had just graduated from Oregon State University, where she had been in a sorority and Wilberger was a college sophomore at Brigham Young University. 

Both women had blonde hair and blue eyes, and they were close to the same age.

However, no solid evidence has ever been discovered to tie Courtney to Eggleston, whom police now believe did not flee on her own accord. 

Eggleston had no history of mental illness or runaway behavior and she was close to her family, which included her parents, three sisters and four nieces and nephews. 

Her passport has never been located.

Foul play is suspected in Eggleston's case, which remains unsolved.

'We have no updates to offer on this case. The unsolved case remains profiled on our website, which includes information about how to provide information to detectives,' a spokesperson from the Portland Police told the DailyMail.com.