Tammy J. Zywicki, 21, disappeared on August 23, 1992. She left Evanston for Grinnell, Iowa, but never arrived.
An ISP trooper found Zywicki's abandoned car, a 1985 White Pontiac T1000, later that day. That evening, Zywicki's mother called ISP and told them that her daughter had not arrived at school.
Zywicki was found stabbed to death found along Interstate 44 in rural Lawrence County, Missouri, which is located between Joplin and Springfield, on September 1, 1992.
ISP said a semi was seen near Zywicki's vehicle. The truck's driver was described at the time as a white man between 35 and 40 years old who is over 6 feet tall with dark, bushy hair.
Special agents are now looking for information about Theresa "Teri" Belenske, who may have a connection with the truck driver. ISP said Belenske, whose maiden name is Vega, was known to hitch hike and may have been traveling with the truck driver at some point before Zywicki's death.
ISP said Belenske is a person of interest, not a suspect. She would have been 32 years old at the time of Zywicki's death, and she passed away in 2014 at 54 years old.
Special agents are looking for information about Belenske from the late 1980s through the mid-1990s. Belenske has ties to cities in California, including Oceanside, Vista, Pomona, San Bernadino, and Fontana.
Police asked anyone with information about Belenske or Zywicki's case to leave a crime tip at ISP Investigative Tips page or call 1-800-CALL-FBI. Callers can remain anonymous.
The FBI is offering a reward of up to $50,000 for information leading to the killer's identification.
Police released a photo of Belenske taken in 2009, along with an AI-generated image of what she may have looked like in 1992.
Police also released photos of Zywicki and some of her property known to be missing.
Missing items include a Cannon 35mm camera and a Lorus brand musical wristwatch, which played the tune "Raindrops Keep Falling On My Head." Also taken was a red and white soccer patch monogrammed with "St. Giles Soccer Club, Greenville, SC."
Zywicki's case remains active as ISP and the FBI continue to explore new leads, examine 200 pieces of evidence, and retest items with modern DNA technology.
The video in the player above is from a previous report.