Stacy McCall's mom says she still can't figure out why her daughter would have left all of her belongings behind

After 27 Years, Springfield 3 Crime Scene Still Troubles the Mother of One of the Missing Girls

It has been more than 27 years since Janis McCall has seen her daughter Stacy — and McCall remains puzzled by what she found at the home of her daughter’s friend before the disappearance.

“In the bedroom, I became concerned because she did not take her purse with her, her driver’s license or anything. She did not take her makeup bag,” McCall says in tonight’s premiere episode of PEOPLE Magazine Investigates. “I saw her shorts. They were folded up nicely.”

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The clues left behind have bothered McCall since June 6, 1992, when Stacy, 18, graduated from high school and prepared to attend parties with her friend Suzie Streeter, 19.

The pair stayed the night at the house of Suzie and her mother, 47-year-old Sherrill Levitt.

The next morning, Suzie and Stacy had plans to go to a water park with other friends. But the friends never heard from them, and after Janis couldn’t reach her daughter, she drove to Suzie and Sherrill’s home hoping to find her.

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Stacy’s car was parked outside, but no one answered the door. After opening the unlocked door, she walked into an empty house. The television was on and the three women’s purses sat lined up on the floor. Stacy’s clothes from the night before were folded neatly in a bedroom.

The trio is still missing, and the unsolved case of the so-called “Springfield Three” is explored in the season premiere of People Magazine Investigates on Investigation Discovery, airing tonight at 10 p.m. EST.

To this day, the case brings in several leads a week, according to the Springfield Police Department.

“Whoever is responsible for this can’t take back what happened, but they can help bring some closure to the families while they’re still alive,” Officer Rick Bookout tells PEOPLE.

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At the beginning, McCall thought she would be reunited with her daughter, but the days turned into years and eventually decades. McCall says she’s angry and hopes to someday find justice.

“Why would she go somewhere and leave her stuff?” McCall asks. “Why didn’t she call me? Where is she?”