The father said the Somali girls saved $2,000 before stealing another $2,000 from their parents to pay in cash for tickets to Turkey at Denver International Airport's Lufthansa counter. Most airlines do not place travel restrictions on passengers over 12. The missing money was documented in one of the reports filed by the families.
About 10:30 a.m. that day, an Aurora high school called the father to say his daughter had missed a class. When he called her, the teen told him it was a mistake and that she was only late, he said.
He soon realized she wasn't being truthful after a son who attends the same school said he didn't know where she was. When he saw a troubling post from his daughter on Twitter, the father was shocked.
She tweeted: "Please please please make (prayer) for me wherever you are. I truly need it, may Allah bless you all."
The father said he knew it meant trouble, and he asked his son at home to check the family passport collection, only to find his daughter's gone. He called the sheriff's office and the FBI.
The father appealed to his daughter on Twitter, saying: "Please if you read this tell me where you are? We are so worried about you #Isis #raqqa #Colorado."
Raqqa is a city in Syria that is considered the capital of the Islamic State.
Federal officials located the girls on a Frankfurt-bound flight and alerted German authorities. The father said federal agents waited with him all night until his daughter was located and returned.
"It's something that's unbelievable," he said of reuniting with his teen daughter two days after she left. "It's indescribable. You just lost somebody very, very, very dear to your heart, and then she came back."
"I'm very sure if my daughter crossed into Syria, I was never going to see her in my life," he said. "She would be gone."
It wasn't until he saw tweets and Facebook posts that he connected the dots and discovered she was heading to Syria, he said.
"It's very simple that these girls are a victim of some online person," he said. "They come back and they realized that when (federal agents) talked to them. They realized that they made a mistake."
There were no previous indications of the girls' plans, the father said, adding that his daughter "never lied to me. She is always a good girl." He said Twitter is a dangerous place for kids that he blames for his daughter's apparent radicalization.
The family says it has pulled their daughter out of school and is trying to piece their lives back together.
"We're just scared from the media," he said of not sharing his story earlier. "Hundreds of people knocking on our door. Our neighbors are not feeling OK. The management are not feeling OK. We don't want to get attention to ourselves anymore."
During the search for his teen daughter, the father sought help from state Rep. Daniel Kagan, D-Cherry Hills Village. Kagan, the chairman of the House Judiciary Committee, pushed the matter up the chain of command.
"He was worried sick," Kagan said Monday. Kagan said as he listened to the man's story, he became extremely concerned.
"This is a girl in a good family with good strong family roots," Kagan said.
Officials say they believe the girls were recruited online by a "predator." An FBI official told The Associated Press they were reviewing the girls' computers.
BuzzFeed on Monday found that two of the girls had created secondary, now-deleted, Twitter accounts where they interacted with purported Islamic State members and wrote about their extremist views.
One teen tweeted: "Those who identify as 'gay' and 'Muslim' at the same time deserve death."
The girls have not been charged with any crime, although the FBI and Colorado's U.S. attorney's office say they are reviewing the matter.
Some former federal officials say it's highly unlikely the girls will be charged.
"It is really, really difficult in the federal system to prosecute a juvenile," said Jim Davis, former special agent in charge of the FBI's Denver division. "I'm having a hard time remembering it ever being done."
Davis said the main difference between the recent inquiry and the case of Shannon Conley, 19, of Arvada is age. She pleaded guilty to terror charges in federal court last month after she was stopped at the Denver airport as she attempted to board a flight overseas.
"I think the primary focus of the investigation now is to see who is on the other end of this," Davis said of the case of the three girls.
Jeff Price, an aviation expert and Metropolitan State University assistant professor, said there were red flags that should have been raised when the girls bought their overseas tickets with cash.
"A ... kid walks up to the counter with cash? With any airline person, that should create their own internal red flag," he said.
Staff writer Laura Keeney contributed to this report.