Forty-four-year-old cases are difficult to solve; potential witnesses have died, evidence may be long-gone and initial investigators could be retired. For the families of missing persons, though, the fight for justice has no expiration date.

“I try to be supportive of the investigation,” Laura Hinckley told Dateline. “I try to keep on the investigators’ heels.”

Sheryl Ann Tillinghast

Hinckley’s sister Sheryl Ann Tillinghast, then just 17 years old, was last seen September 24, 1973 in Wassaic, New York, a small town on the New York-Connecticut border.

According to her family, Sheryl left $150 worth of paychecks and all of her belongings at her apartment. At the time, Tillinghast hadn’t been living at home for almost a year; she’d been sent to a reform school for girls after pleading guilty to a possession of marijuana charge. The reform school burned down, though, and Tillinghast was sent to the Wassaic State School for Mental Defectives.

“She graduated from that school, but, because of her relationship with my mother – which wasn’t good – she decided she didn’t want to come home,” Hinckley said. “She stayed up there in the Wassaic State School area, got an apartment nearby and worked at the school’s laundry.

Despite the strained relationship between mother and daughter, Hinckley says her mom grew worried when Tillinghast didn’t show up at home for a planned family birthday party.

“My mom called the school and asked where she was. The school told her Sheryl was an adult and didn’t have to come home if she didn’t want to,” Hinckley told Dateline. “My mom basically decided that was that, and never looked into it further.”

Hinckley said because of the dynamics of the family, none of her siblings questioned their mother’s actions and therefore didn’t follow up with the police, themselves.

“She was very authoritarian toward us,” Hinckley told Dateline. “My siblings in the family were afraid to do anything outside of what my mother said.”

There’s a difference, though, between not actively searching for someone and not even reporting them to the police as a missing person.

“I knew my mother rarely spoke with Sheryl and they had their issues, but surely she’d reported her missing. Surely the police had been looking for her all this time,” Hinckley thought. “I was only nine years old when she went missing, so all these years I thought they were looking for her and were going to find her one day.”

One day in 1998 – 25 years after Tillinghast was last seen – Hinckley and her siblings discovered the unimaginable: Their sister had never been reported missing to the police.

“I was shocked,” Hinckley told Dateline. “She was a 17-year-old child who disappeared into thin air and left behind her belongings. The school had a responsibility to call the police. My mother should have fought for her from the time she knew Sheryl disappeared until she took her last breath.”

The unfortunate discovery happened by accident.

“A sheriff in Chester County, New Hampshire had an unidentified remains investigation of a female,” New York State Police Senior Investigator Tom Crowley told Dateline. “The sheriff’s department in New Hampshire saw a civilian report in New York [of Sheryl Ann Tillinghast and] they thought it would be a possible match.”

Investigator Crowley took the case over from Senior Investigator Allen Dombrowski, who retired in 2012. According to Investigator Crowley, Investigator Dombrowski immediately “had to contact all the agencies in this area and downstate where she was last seen, and he determined there hadn’t been an investigation at all – there was no missing persons report for Sheryl.”

Hinckley says it wasn’t only their mother who let Tillinghast down by not reporting her missing. She told Dateline her sister had an after-care case worker who also should have taken control of the situation.

“No missing posters were put up. No searches were conducted,” Hinckley said. “All those adults let her down by not reporting her missing.”

By 1998, though, the damage done by not having an initial investigation was almost impossible to overcome.

“It’s a bad place to start, obviously,” Investigator Crowley said. “But [Investigator Dombrowski] did the best job he could trying to figure out what happened by searching through records to piece together a timeline.”

Despite her failure to report her child as missing, Tillinghast’s mother was never suspected of having a role in her daughter’s disappearance, according to Investigator Crowley. With few leads to go on, according to the investigation’s records, members of the New York State Police intelligence unit combed through police databases to see if Tillinghast had even existed after the date she was last seen.

“They looked at pay stubs, taxes, her social security number…” Investigator Crowley said. “There was no activity at all.”

“He exhausted every avenue he could to try to find her,” Hinckley said. “Then he asked me if me and my sister could give DNA samples so they could compare our DNA to unidentified bodies they found.”

Despite the passage of time, Tillinghast’s case remains open and she is still listed on the New York State Police website as a missing person.

“There were physical searches of her school conducted with canine assets. We also did multiple interviews with people,” Investigator Crowley told Dateline. He said that while the searches did not produce any results, the interviews helped establish what her life was like at the time she disappeared: who she hung around with, what she was doing, etc.

“There were reports she had a boyfriend at the time, but he is now deceased,” Investigator Crowley said. “Obviously we would’ve liked to interview him, [but] we continue to try to find people who knew Sheryl who could add another piece to the puzzle.”

Both investigators and family believe some pieces of the puzzle have already been put together.

“We think she is deceased, [but] absolutely the body could be out there,” Investigator Crowley told Dateline. “That’s the direction our investigation is heading. But any lead that comes in -- we take that information and we pursue it to its end.”

Hinckley agrees, adding she does not believe her sister left on her own free will.

“I always had a feeling something really bad happened to her,” Hinckley said. “She would at least try to get in touch with her siblings, because she loved us very much. There’s no way she would’ve just left.”

Since Tillinghast was the third oldest of eight children, Hinckley said she often took on a lot of the caretaking.

“She was a mothering figure to us. She cared about us, babysat us,” Hinckley told Dateline. “She was the one who, at Christmastime, would make Christmas cookies with us.”

Authorities say there have never been any suspects named in the case, but there could have been had Tillinghast been reported missing at the time of her disappearance.

“As soon as you suspect that someone is missing and the circumstances are suspicious, you should contact the authorities. It’s important,” Investigator Crowley said. “And you can’t be afraid or hesitate to follow up. I tell anybody I deal with in these circumstances: they can tell us as many times as they want, as often as they want.”

Sheryl Ann Tillinghast would be 61 years old today. She is described as being 5’3” with brown hair and brown eyes. Anyone with information on her case is asked to call the New York State Police Tip Line at 1-866-723-3697.