On Thursday, a work crew found skeletal human remains under the New River Gorge Bridge near Fayetteville, West Virginia, which authorities believe could be linked to Robert's cold case, a spokesperson for the West Virginia State Police confirms to PEOPLE.
"This has been hard on us for the last 18 years," Robert's father, Michael Kovack, tells PEOPLE. "And it's still hard. It's bad."
Since Thursday, the West Virginia State Police and the U.S. Park Service have been processing evidence at the crime scene and trying to positively identify the remains, according to a press release issued by the West Virginia State Police.
The work crew discovered the decaying bones under the bridge on U.S. Route 19 near Fayetteville, near where Robert's Geo Tracker was found abandoned on Sept. 22, 1998 – three days after he was last seen.
"It's been festering and now it's all opened up again," says Michael. "I went through this 18 years ago and it's like opening an old sore up again."
His disappearance became one of the most baffling cold cases in West Virginia. Michael and his family still have no answers.
"We don’t know anything," he tells PEOPLE. "They found some remains and we are just waiting now."
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Details of Case Don't Add Up for Robert's FatherAt the time of his disappearance, Robert's mother, Jacqueline Kovack, called police after she tried contacting him unsuccessfully for three days.
Robert's Geo Tracker was out of gas when it was found abandoned, which his father finds odd considering Robert knew the area and wouldn't have found himself far from a gas station with an empty tank.
"If you made a trip 50 times and you knew where the gas station was, would you run out of gas? That's what I'm saying. They said his car was out of gas. I don’t believe that he was driving that vehicle."
Helicopters scoured the area while police and volunteers searched on the ground and in the water for Robert, but came up with nothing.
Reports at the time of his disappearance said that Robert was planning to visit his family in Rivesville, West Virginia, the weekend he vanished. But Michael says that Robert always called before he came home, but didn't in this case.
In response to rumors that Robert might have tried to run away, Michael points out that Robert, a teaching assistant at Virginia Tech, had $1,500 in his bank account. "Now, if you ran away, would you leave $1,500 in a bank account?" he says.
Not a day goes by when Michael and his wife, Jackie, don't think of their son.
"He was a good guy," he says of Robert, who worked for Habitat for Humanity. "He was my son. He was happy-go-lucky. He was hard working."
The investigation remains ongoing.