"A case never closes until the child is found," said Bob Hoever, director of the center's missing children division.
The oldest Utah case is that of Reed Jeppson, who was 15 in 1964 when he took his dogs for a walk through his Salt Lake City neighborhood. He and the pets never came back.
A lot has changed since then, said Paul Murphy, Utah Amber Alert coordinator. Law officers are better trained to handle such cases, including what to look for and how to implement an immediate search, with tasks delegated as soon as officers arrive on the scene.
Search efforts are planned in advance, with jurisdictions dissected into grids assigned to searchers. And some of those searchers come from local, specialized teams such as the Community Emergency Response Team and Child Abduction Response Team.
In the 1980s, a missing child had about a 60 percent chance of being found; the recovery rate today is 97.5 percent, according to Hoever.
Another factor: Now, more than ever, the public is getting involved.
In 2002, Utah adopted the Amber Alert to enlist citizens in child abductions. Since it was first used in the disappearance of Elizabeth Smart in 2002, the Amber Alert has helped recover 17 lost children in Utah, Murphy said.
Utah instituted a missing endangered advisory in 2005 for people like Brooklyn who are missing and thought to be in danger but who aren't known to have been abducted. The advisory is like an Amber Alert except that it does not appear on electronic roadway signs or cut into broadcast programming. In the 103 times it's been used, the advisory directly led to the safe recovery of 81 people, Murphy said.
In Herriman, the advisory helped attract more than 1,000 people to look for Brooklyn.
"When a child's abducted, it's like trying to find a needle in a haystack. When you're trying to find that child, the more people you have looking, the smaller that haystack gets," Hoever said.
But sometimes, information dries up, leads go nowhere and the trail goes cold, said Lt. Matt Johnson, spokesman for the Spanish Fork Police Department. In 1995, 15-year-old Kiplyn Davis disappeared after her lunch break at Spanish Fork High School. After an initial investigation, the case stalled.
Her disappearance occupied the city's collective mind for more than a decade. Merchants displayed Kiplyn's missing-person poster in their windows for years, replacing them after they weathered.
New information revived Kiplyn's case in 2003, and eventually a former classmate admitted he saw someone whom he wouldn't name beat her with a rock and move her body. Kiplyn has never been found, but the classmate, Timmy Brent Olsen, is serving up to 15 years in prison for second-degree felony manslaughter.
By the time a snowstorm rolled in Thursday during the search for Brooklyn, police had decided to end their already comprehensive ground search for the girl, sending hundreds of volunteers home and moving instead to a specialized, targeted search with their detectives. A few hours later, Brooklyn called her grandmother from a Walmart in South Jordan.
Unified Police Lt. Justin Hoyal believes that the involvement of emergency responders, volunteers and media in the search for Brooklyn may have forced the hand of the person who was harboring her. He agrees that children today have a better chance of being found.
Law enforcement still looks for ways to improve the system. Utah updated its Amber Alert to a faster system in October and tested it Sunday, including radio and television participation, to make sure everything works as it should.
The Amber Alert or missing endangered notifications were developed too late to help some of the 13 children on the national center's list, not all of whom are mysteries. In 2004, Brenda Gomez's father took the 12-year-old from her mother, who had legal custody, to live with him in Mexico. Brenda is alive and well, as far as the police know, though the separation is no easier for her mother, said Logan police Lt. Brad Franke.
But some disappearances are plagued by unanswered questions.
Last year, Frank Frost told The Salt Lake Tribune that his family never gave up hope they would find his sister, Debra Frost. The 17-year-old went missing in July 1984, and the man police suspected had a connection to her disappearance has since killed himself.
The family of Reed Jeppson still holds out hope for an answer as well, though they've held on longer than anyone.
Last September, police converged on a gully near Reed's home after cadaver dogs indicated a body. After a long day of digging, with his family huddled tight around the site, nothing turned up.
Though disappointed, Salt Lake City detectives and the Jeppsons said they aren't giving up. Neither did Brooklyn's searchers. As Hoyal said as the sun set on the first day of the search, "We'll keep looking until we find her."
Twitter: @mikeypanda Utah's missing children
Garrett Bardsley • 12 years old when he disappeared in 2004 during a Boy Scout outing in the Uinta Mountains. Last seen in the Cuberant Lake area.
Acacia Bishop • 19 months old in 2003 when she was kidnapped from her great-grandmother's Salt Lake City home by her mentally ill grandmother, 38-year-old Kelly Lodmell. Lodmell claims she drowned the baby in the Snake River at Idaho Falls, but the body was never found. There is hope Lodmell passed the child to one of her friends.
Elizabeth Clancy • 16 years old when she disappeared from her St. George-area home in 2012. Listed as an endangered runaway, she may have traveled to San Diego, Calif.
Kiplyn Davis • 14 years old when she disappeared in 1995. Last seen at Spanish Fork High, she may be the victim of a homicide, but her body has never been found.
Jason Dennis • 18 years old when he went missing in 2002 from the St. George area. He may have traveled to Salt Lake City, Nevada or Southern California. He was suicidal and took a .22-caliber Jennings handgun with him.
Debra Lee Frost • 17 years old when she disappeared in 1984. Last seen at Mountain Bell Plaza in downtown Salt Lake City. She planned to walk or hitchhike to a home near 1200 South and 1600 West but never arrived.
Brenda Gomez • 3 years old in 2004 when she disappeared while on a visit with her father in Logan. She may be with her father, and they may still be in Utah or may have traveled to Mexico.
Reed Jeppson • 15 years old when he disappeared in 1964. He was last seen walking his two German shorthaired pointers in the east bench area of Salt Lake City.
Lucero Jimenez • 14 years old when she disappeared in 2009 from West Valley City. Listed as an endangered runaway, she was last seen leaving her school.
Carlos Reyes • 7 years old in 2006 when he was taken by his noncustodial father for a visitation and never returned. The vehicle was located abandoned in San Diego. It is likely they are in Mexico.
Maria Salazar • 14 years old when she disappeared in 2012 from the Snowville area. Listed as an endangered runaway, she may be in the company of an adult male. They may have traveled to Mexico.
Rikki Tabbee • 17 years old when she disappeared in 2012 from Roosevelt. Listed as an endangered runaway, the girl may be in the company of an adult male.
Jade Thornberg • 16 years old when she disappeared from Sandy in 2012. Listed as an endangered runaway, she may be in the company of an adult male, and they may still be in the local area.
Sources: National Center for Missing and Exploited Children and the Utah Bureau of Criminal Identification