Spierer went missing about 4:30 a.m. June 3, 2011, after a night of partying with friends in downtown Bloomington, Ind. It's been reported she was walking home alone toward her Smallwood Plaza apartment after a night out at Kilroy's Sports Bar and 5 North Townhomes.
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Robert and Charlene Spierer said on their website, www.findlauren.com, Thursday that they understand their daughter is likely dead even though no remains have been found and no arrests have been made.
"We have no doubt that when Lauren is found, the next chapter of this horrible nightmare will begin anew," the couple said.
But they stressed that they are determined to find out what happened to her, saying they are "Unwavering in our desire to find our daughter and see that justice is served for a life ended too early."
The Spierers have said repeatedly they believe one or more of Lauren's friends who was with her the night of her disappearance knows something about what happened to her and are holding out on investigators.
The Spierers spoke to People magazine for an interview in this week's issue and have been in contact with the producers of NBC's "Dateline" about a possible segment on their daughter's disappearance.
A phone message left at the Spierers' Greenburgh home Thursday was not immediately returned.
Anyone with information about Spierer's case is asked to call the Bloomington Police Department at 812-339-4477 or Beau Dietl & Associates, the family's private detective firm, at 800-777-9366.
Tips can also be submitted at firstname.lastname@example.org or by mail at Find Lauren, P.O. Box 1226, Bloomington, IN 47402.
With The Associated Press