Distraught, Pratt said he spent the next three years working with the consulate in Ecuador, trying to find her body, with no success.
Over the years, Pratt says, he became bitter and withdrawn, angry at Francesca's mother and at himself for letting his daughter leave the country. "I blamed myself, I blamed her and I blamed God," he says.
He spent Francesca's birthday every year looking at her photo. He wrote her letters and burned them, he says, so the smoke would rise to heaven and she could read them.
Then, earlier this year, out of idle curiosity, Pratt searched for his name on Google.com. What he found, he said, left him in shock.
"This message is for Dirk M. Pratt, I'm looking to make contact with him," read a note posted in November 2007 on an Internet message board. "I'm his daughter."
Thousands of miles away in Ecuador, Francesca Pratt grew up thinking her father died in a diving accident. But something tugged at her, a vague feeling in her heart, she said, that he was alive.
Francesca began to search for him, eventually moving to the United States. "I needed to know about him," Francesca, 30, said in a tearful interview with ABC News. "I need to know if I have a family."
After seeing his daughter's online post, Dirk Pratt responded on the same message board. When he didn't hear back, he sent a letter to a newspaper in Quito, looking for her. The letter said he loved his daughter and not a day had passed when he didn't think of her.
Dozens of people responded to Pratt with leads; some of them said they knew his daughter's family.
"When I first realized she was alive, I had a mission," he said. "My feeling was I was going to do whatever it took to find my daughter. And that was my mission and that's all I could think of. It's I'm going to find my daughter and nothing's going to stop me from finding my daughter."
"I was overwhelmed by this feeling of seeing my baby," he said.
The pair reunited this week for the first time in 27 years. Pratt met his daughter, now 30 and pregnant with her own child, at the Seattle airport.
"You go through a thousand feelings all at once," Pratt said. "They hit you all at once -- happiness, joy, fear."
Daughter: 'So Happy' to Find My Dad
"I want to cry, I want to scream, I don't know what really I wanted to do," Francesca said of her feelings when she finally saw her father for the first time in all those years.
"I am so happy. I was happy yesterday when I saw him the first time. It was amazing, really amazing."
"I know he loves me and I know I love him," she said. "So that is the most important now."
Francesca said she plans to live with her father for now, and to get to know him.
Pratt wrapped his daughter in a hug. "I got my baby back," he said.