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A full year after a 20-year-old Indiana University student disappeared from her college town, the woman’s parents are down to just “this little bit of hope” she could still be alive.

“It’s a remote possibility that she’s alive and a greater possibility that she’s not,” said Robert Spierer, whose daughter, Lauren, disappeared early Friday, June 3, 2011, near the school’s Bloomington campus.

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Spierer, of Greenburgh , N.Y., was last seen early that morning on the intersection of 11th Street and College Avenue in Bloomington, according to the woman’s acquaintance and college classmate Jay Rosenbaum.

Rosenbaum claims he watched the petite, blonde-haired student walk from his building toward her off-campus apartment complex some three blocks away around 4:30 a.m. the morning she disappeared.

Rosenbaum’s last reported sighting of Spierer followed a night of partying among a loose group of college friends and acquaintances.

Robert Spierer believes his daughter, who took medication for a heart condition, could have been drugged at Kilroy’s Sports Bar, a popular college hangout with an outdoor sandy area designed to look like a beach. Authorities reported that Spierer left her shoes and cell phone behind there.

“She could have been given something in her drink, unknowingly, that made her almost incapacitated,” Robert Spierer told FoxNews.com.

Spierer, a fashion merchandising major who had just completed her sophomore year, left her apartment complex around 12:30 a.m. June 3 with a friend, David Rohn, to walk to Rosenbaum’s apartment. Once at Rosenbaum’s residence, Spierer met a male acquaintance – Corey Rossman – who lived two doors down from Rosenbaum.

Rossman, who was reportedly on a “no trespass” list at Spierer’s building over a 2010 incident that had occurred there, left his building with Spierer and headed for Kilroy’s Sports Bar. Police said Spierer and Rossman entered the bar at 1:46 a.m. and left at 2:27 a.m.

Many questions surround what happened next.

Surveillance video captured Rossman and Spierer entering her apartment building – known as Smallwood – shortly after leaving the bar. Rossman reportedly claimed he was injured in a fight with other male students on the fifth floor of the building and remembers nothing of what happened during and after the incident. At 2:42 a.m., Spierer is seen leaving her building with Rossman and walking up an alley toward Rosenbaum and Rossman’s apartment complex.

Spierer, who police say dropped her keys and identification card on the way, spent some time at the men’s building before leaving at 4:30 a.m., according to Rosenbaum, who claims he watched from a balcony as she walked toward her apartment. Spierer was never seen or heard from again.

Do the young men who last saw Spierer alive know her fate? Or did she fall victim to a stranger abduction as she walked in the dark, alone and inebriated, a short distance toward her home?

Bo Dietl, a New York-based private investigator hired by the Spierer family, said “all options remain on the table.”

“At this point, no one has been eliminated,” Deitl told FoxNews.com. “Everyone is still a suspect as far as knowing what happened to Lauren.”

Robert Spierer and his wife, Charlene, say they believe the group of male students – including Rossman’s roommate, Mike Beth – know more than what they’ve told investigators.

“Obviously we don’t feel they’ve done everything in their power to be of assistance to us,” Robert Spierer said.

Spierer’s disappearance touched off a massive search by air, land and water for any trace of the young woman. The Bloomington Police Department said Thursday it receives on average about two to three “credible” leads weekly in the case – totaling more than 2,600 tips to date.

Last August, the FBI scoured the Sycamore Ridge Landfill in Pimento for any clues in the case. Authorities are also probing a possible connection between Spierer and accused serial killer William Clyde Gibson, a 54-year-old convicted sex offender linked to the deaths of at least three women more than 100 miles away. The remains of one of the victims – 35-year-old mother Stephanie Kirk – were found buried in the backyard of Gibson’s home in New Albany, Ind. Police have so far determined no connection between Spierer and Gibson.

Lauren, whom family described as “vivacious” and “loving,” had a an ability to “make everyone feel very comfortable,” her mother said.

Spierer, who is 4-foot-11 and weighs 95 pounds, has blonde hair and blue eyes. She was last seen wearing black pants and a white top.

A $250,000 reward is being offered for any information leading to Spierer’s whereabouts. Anyone with tips in the case is urged to contact the Bloomington Police Department by phone at 812-339-4477 or by email at policetips@bloomington.in.gov.

To learn more about Spierer’s disappearance, visit FindLauren.com