Lauren Spierer of Greenburgh, N.Y., disappeared almost two years ago in Bloomington, Ind. The defendants in the lawsuit -- Corey Rossman, Mike Beth and Jay Rosenbaum -- were with her in the period just before she vanished, FoxNews.com reported Friday.
Spierer, who was apparently extremely drunk, was last seen in Rosenbaum's apartment in the early morning hours of June 3, 2011. Rosenbaum said he tried to convince her to sleep on a couch and, when she refused, watched her begin the short walk back to her apartment.
Spierer and Rossman were seen together earlier in surveillance video that showed them at a popular bar in downtown Bloomington, entering her apartment building and then returning to his apartment, in the building where Rosenbaum also lived.
The parents filed the lawsuit last month in Indiana.
"Any parent in search of information about a missing child would use every resource available to them," their lawyer, Jay Barclay, said. "Therefore, we intend to use the rights afforded by the civil justice system to obtain answers to questions that have gone unanswered for too long. We fully expect that those with relevant information will cooperate with this process."
Robert Spierer, in an interview with Fox last month, said he is unsure whether his daughter left Rosenbaum's apartment.