Since 2005, Florida has identified and reported 7,849 children missing from state care, Allen said, and, of those, 7,221 were runaways. The state has 214 active cases: 209 runaways and five family abductions.
But in the majority of missing foster children cases, "I think the cause for this is systemic," Allen said.
"I think, overwhelmingly, they don't get into the system," he said.
In Connecticut, a state Allen identified as having particularly strict regulations regarding the identification of children in state custody, the state typically notifies the state police, which in turn is charged with reporting the case to the National Center for Missing & Exploited Children.
"I'm sure we would not identify them as foster kids," State Department of Children and Families spokesman Gary Kleeblatt said, "because of our confidentiality issue."
But Connecticut State Police Lt. J. Paul Vance said that finding the children trumps privacy concerns.
"We don't care," he said. "Our objective and our goal is solely to locate that missing child."
But even he conceded that police are also hesitant to identify the child publicly as a foster child, though for different reasons.
"I don't want to tag them or label a child, if you will, than anything more or less than a child," he said.
But there are other, often more serious, challenges that come with searching for a foster child.
"There might not be family photos, there might not be some things that we need to get the ball rolling," Vance said, listing DNA samples, family members to interview or family history.
State police, Connecticut's clearinghouse for all missing persons cases, are also often hampered by a lack of good information about when and where the child disappeared, he said, a problem compounded by a large number of cases and frequent emergency transfers.
But even when states do their best to publicize a missing child, it often doesn't garner the same frantic headlines blasted across the country as for the high-profile disappearances.
Earlier this month, the case of missing 4-year-old Alisa Maier, who was snatched from her Missouri front yard, was solved within 26 hours after intense media coverage, neighborhood search parties and the pleas from her mother, who even tried to chase down the car carrying her kidnapped daughter.
Alisa was found alive at a car wash 80 miles away. Her suspected captor shot and killed himself.
In all such cases, the children's biological parents were "out there fervently pleading for help in the search for their children," Allen said.
"It's a lot harder," he said, "for a state social worker to have the kind of impact on the public when the child is missing as opposed to if it's a mom and a dad."
A case that defied all convention, however, was that of missing 7-year-old New York City boy Patrick Alford, whose status as a foster child hasn't stopped his foster parent and the state from getting his case put on everything from local newspapers to national websites to a segment on "America's Most Wanted."
Patrick, Allen said, had attempted to run away before to find his biological mother. In January, he made another run for it and got away while his foster mother was taking the trash out. He left in the dead of winter, with no extra clothes and no supplies.
She immediately called both state authorities and the police, who in turn notified the National Center for Missing & Exploited Children. He has never been found.