They're well aware that their daughter may be dead, so their frantic desperation has turned to a calm and steady resolve. Moving into their own apartment in downtown Bloomington, the couple said they have no plans to return full time to Greenburgh until this case is solved.
"Because we don't know what happened to her or where she is, we're not giving up hope that she could be alive," said Robert Spierer, who, with his wife, continues to work from dawn until past midnight on a daily basis to try to get answers.
So far, they feel, they've failed. Three months since vanishing, the 20-year-old remains missing, and police have identified no suspects.
But this reality is only emboldening them. As students have returned to classes for the new school year, they ran a full-page letter in the campus newspaper and led efforts to post new "missing" fliers on every light pole and building in Bloomington. Even roads miles outside of the city are lined with billboards, advising the public to call a tip line and to visit the family-backed website, www.findlauren.com.
Charlene Spierer marks the three-month anniversary today by publicizing a new letter she wrote in which she shares her deepest thoughts about the day her daughter went missing.
"We constantly try to come up with ways to keep Lauren's disappearance in front of everyone's mind," she said.
They announced another event they're planning for Sept. 22, a concert featuring two live bands on the main lawn of the IU campus.
"Our goal is to make it big enough to generate media," she explained.
The transformation of the couple, once happily engaged in their suburban community of Edgemont, began June 3, three months ago today, when they received a telephone call that Lauren never made it home from a night out with friends.
In early news conferences with Bloomington police, the couple appeared physically and emotionally drained, as they described living out their "worst nightmare."
In the early days, Charlene would end the news conferences with an appeal to her daughter that she would never leave without her.
Most thought they would leave, eventually, and they did return to Edgemont late last month after joining police at a landfill for the first days of a massive search of thousands of tons of refuse.
No evidence was found.
Then, after spending a few days in Westchester with their older daughter, Rebecca, on her 25th birthday, they returned to Bloomington, taking the last flight out of La Guardia Airport before Hurricane Irene struck.
With the new school year, they've been on a mission to make every student aware that Lauren is still missing and that efforts to find her and whoever may have been responsible for her disappearance will not end until they have answers.
During the day, they help plan events, meeting with staff and students at the college, and working the phones and Internet to communicate with supporters. They also discuss the case with investigators.
"We meet with police regularly," Robert Spierer said, describing himself as "in the loop" on the investigation.
At night, they click through emails and check all the news on the case, whether with mainstream media or blogs circulated by a network of supporters and others who discuss real news and rumors related to the disappearance.
"I read everything," Charlene Spierer said.
At times, the Spierers notice comments online that appear to be tips, including one speculating that Lauren Spierer was taken to another state. They share them with police, and officers track them down.
"There's a disconnect between communications provided to the Police Department and the social media chatter related to Lauren's case," her father said. "This (chatter) is not going to the Police Department, and we don't know why."
The parents spend countless hours backtracking stories and other speculation on the case to determine what might be true.
Much of the speculation revolves around the last people known to have interacted with their daughter the morning she vanished.
The parents are increasingly skeptical of these "friends."
They noted that police have asked all of the persons of interest to take lie-detector tests but that "just one person did." They wouldn't name that person, keeping details that police share with them private.
The parents are also aware that there is a certain backlash against all of the attention the case is getting.
They've read negative comments online from people who are fed up, concluding that Lauren is dead and that the parents should just give up and go home.
Charlene Spierer's response: "If the roles were reversed, would they just pack up their bags and leave?"
They also know that some locals are sick of all the "missing" posters around town. Some people, including students tired of the saturation, tear them down.
Her response: "If I could blanket the world with Lauren's poster, I would.
"We have to do it," she said firmly. "We have to do it."
But far more people are supportive of their efforts, saying their pressure has made this a national story, generated leads and prompted an unrelenting investigation.
"If it were my child, I wouldn't stop either," said Rabbi Sue Silverberg of the campus Hillel, of which Lauren was a member.
Silverberg is among an army of supporters who have assisted the Spierers.
"We're private people," Charlene Spierer said of their life before the disappearance. "We find ourselves thrust into this role. This is where we have to be."