Police, family and friends are still searching for Lauren Spierer, the 20-year-old Indiana University student from Westchester who went missing last Friday. Authorities are taking a close look at one person in particular: Corey Rossman, the last person known to have seen her. Police have already given him a lie detector test, but there's one strange problem: Rossman claims he has no memory of their last moments together.

According to friends, the sophomore from Edgemont was out for a late night of partying with friends on Friday June 3rd. Spierer was seen entering her apartment in Bloomington with Rossman, a "male friend", and going back out with him at around 2:40 a.m. They told the Post that Spierer was very drunk at the time, that Rossman was bothering her and that he got angry when they asked him to stop: "He was being overly aggressive...being so belligerent." The two allegedly ended up at Rossman's apartment; he told police that she left at 4:30 a.m. and that he watched her walk away to make sure she was OK. One of Spierer's friends added that even if that was true, it wasn't the best course of action: "She was a tiny girl, clearly very inebriated with no shoes or phone...He never should have let her leave."

Then there was a new wrinkle in the story: Rossman claims he was involved in a fight that night...except he doesn't quite remember. "It is my client's understanding that he was assaulted, but he does not recall the incident," Rossman's lawyer, Carl Salzmann, told Bloomington's Herald-Times newspaper. Salzmann said that Rossman only figured out he had been in a fight after he woke up with bruises and a sore jaw and talked to friends. "Who confronted him, why he was confronted -- once again my client doesn't know...His clock just got cleaned, I guess."

Rossman has already taken a polygraph test. The timeline of events that night are still being ironed out, including whether Spierer was with him when this fight occurred, though Bloomington Police Lt. Bill Parker did say that “Lauren was not involved in any altercation.”

Spierer's father, Robert, is offering a $100,000 reward for any information leading to his daughter's return; police say they have received "several hundred" tips about the case. Various celebrities from Ryan Seacrest to Stephen Colbert are Tweeting about it. If you would like to donate to help find Spierer, you can here.