TAMPA — The latest tip came through Facebook. A young woman wrote to Marlene Aisenberg that she could find no records or photos to document the first five months of her own life.

She knew about the Aisenbergs' daughter, who vanished from a Valrico home 20 years ago this week.

Could the woman be baby Sabrina? She wondered.

In photographs, Steve and Marlene Aisenberg couldn't discount a resemblance to their other two children, now in their 20s. It was enough for the woman to arrange for her DNA to be tested in a private lab, Steve Aisenberg said recently.

"Until we have more information, we're cautiously optimistic," he said.

But as they await word, Aisenberg said the couple tempers their hopes.

It is, after all, one more tip in a long list of leads. There are people who call and say they know someone who resembles Sabrina. There was the one about an unidentified girl in Illinois, excluded by genetic testing.

And there are those who still think the Aisenbergs themselves hold the answers to what happened, despite the spectacular collapse of a federal case that was brought against them years ago.

It was the theory local investigators and prosecutors held for years. Their suspicions culminated in a federal judge's rebuke for a bad faith prosecution.

Along the way, the Aisenbergs were propelled into the national spotlight, and their daughter's saga was forever etched into the history of Tampa Bay.

But they don't dwell on the accusations.

"We can't change the past," Steve Aisenberg said. "All we can do is try to affect the future."

The 911 call came at 6:42 a.m. on Nov. 24, 1997.

"I need the police," Marlene Aisenberg said. "My baby has been kidnapped."

Through sobs, she told a dispatcher she had awoken to find 5-month-old Sabrina missing from her crib. The garage door of their Valrico home was open.

Hillsborough County sheriff's deputies arrived within minutes. They found no sign of a break-in. Nothing was missing except the baby and the yellow blanket that went everywhere she did.

As detectives assessed the circumstances, they took stock of dirty dishes in the kitchen and children's toys scattered about the house. They also noted few photos of Sabrina in the house, but several of the Aisenbergs' older children, William, then 8, and Monica, then 4.

The investigators found the couple's behavior odd, their stories inconsistent. They reviewed a video Marlene took of Sabrina, just days before she vanished. On it, they thought they saw bruises on her face and a patch of hair missing from her head.

Detectives suspected child abuse and questioned the couple intensely.

When it became clear that the authorities were pointing the finger at them, the Aisenbergs hired Tampa criminal defense lawyer Barry Cohen.

"The Sheriff's Office, at the time, was so interested in manipulating the evidence they didn't spend the quality time trying to get to the truth and find the baby," Cohen said recently. "They thought they were guilty and they went out to look for the evidence to support it."

Evidence came in the form of thousands of hours of recordings mined through listening devices that authorities secretly planted in the couple's bedroom and kitchen. When an indictment came in 1999, federal prosecutor Stephen Kunz said the couple was recorded making numerous incriminating statements.

That, Cohen said, was a lie.

As the case heated up, Cohen assembled a team of lawyers who remain some of the region's most well-regarded.

Stephen Romine was still new to the firm when Cohen told him he would be involved in the case. Romine had read about the Aisenbergs.

"The rest of the world saw them through the lens of a TV camera," he said. "We sat there and watched them through grief."

When the team scrutinized the static-filled audio, they couldn't hear many of the statements alleged in the indictment. Other statements were misinterpreted.

Harry Cohen, now a Tampa City Council member (no relation to Barry Cohen), was one of those tasked with listening to the tapes.

"Most of it was just listening to people who are going through the process of grieving," he said. "Of the most incriminating and incendiary statements that the government said were there, those things were not audible."

In one statement, the government quoted Marlene Aisenberg saying "you said to fake it." The defense heard "you spoke to David." In another tape, "the shed" became "they said."

The defense hired Bruce Koenig, a former FBI agent and an expert in forensic audio. After he listened to the tapes, he said he could not hear a single one of the statements prosecutors claimed were the most incriminating.

U.S. District Judge Steven Merryday listened and agreed. The U.S. Attorney's Office later dropped the charges.

The judge made the government pay the Aisenbergs $2.9 million in legal fees and costs under a rarely used federal law that permits compensation to defendants for prosecutions made in "bad faith."

• • •

The Tampa Bay Times attempted to reach investigators and prosecutors about the case. Those contacted either declined to comment or did not return phone messages.

The last flurry of headlines came in 2007, when a jail inmate claimed his cellmate told him he had helped dispose of Sabrina's remains. Despite intense scrutiny, nothing came of the information.

The Times reported that more than $300,000 had been spent on the investigation between 2007 and 2008, far greater than other unsolved cases.

The Sheriff's Office said the agency has worked 15 tips that have trickled in since 2014. Asked if the Aisenbergs remain the focus, sheriff's officials responded in a statement:

"We are following the leads when they come in. The leads have gone in several different directions. We investigate each lead thoroughly and do our best to determine the validity of information provided to the Hillsborough County Sheriff's Office."

• • •

The Aisenbergs moved to Maryland in 1999. They work as real estate agents. Their son, now 28, is a graduate student studying medicine. Their daughter, now 24, works with adults with special needs.

Their trust that Sabrina's disappearance will be solved lies more with the public than with law enforcement, Steve Aisenberg said.

When they get tips, they notify the National Center for Missing and Exploited Children, he said. Every few years, the organization creates an age-enhanced photo, depicting what Sabrina might look like today. The most recent shows her at age 18.

"I still believe Sabrina is out there," Steve Aisenberg said. "Now that she's almost 21, we hope that she'll feel like part of her is missing and she'll try to find it."

Contact Dan Sullivan at dsullivan@tampabay.com or (813) 226-3386. Follow @TimesDan.