(CBS) - The parents of Lauren Spierer, an Indiana University student who went missing last June, say they no longer believe their daughter is alive.
Robert and Charlene Spierer returned to Bloomington, Ind. this week, where they spoke with The Journal News, a local newspaper from just outside New York City, where the Spierer family is from.
When asked during the interview if she believed her daughter was still alive, Charlene Spierer responded, "I don't."
"We're trying to be realistic. We know that if she had the chance to reach out to us, she would have done it," Robert Spierer went on to tell the paper.
Spierer was last seen about 4:30 a.m. on June 3, 2011 at a downtown intersection after a night of partying with friends. A friend she was with that night told police Spierer walked home alone after being at a sports bar and a few downtown apartments.
There have been no clues as to what happened to her. Police and volunteer search efforts - including a search of 4100 tons of trash in a landfill - dug up no new information over the summer.
"It's very frustrating to be talking about the exact same things we were talking about the first 30 days after her disappearance," Robert Spierer told The Journal News.
Spierer's parents also said they were frustrated with what they see as a lack of cooperation from two IU students, Jay Rosenbaum and Corey Rossman, who were reportedly with her the night she went missing.
Robert Spierer asked the parents of the two students to "take their sons to the police station and allow for the law enforcement to (perform) polygraphs."
Although most of the persons of interest in the case will graduate in the spring, Robert Spierer told the paper that there is no "deadline on a person's conscience."