"There is no evidence to support the claims that this was a stranger abduction or an abduction at all," Vallejo police said in a statement. "Given the facts that have been presented thus far, this event appears to be an orchestrated event and not a kidnapping."
Denise Huskins had indicated she would talk to detectives after reappearing outside her father's apartment in Southern California earlier in the day, and the FBI had arranged to have her returned to Northern California via jet, police said.
But they are now unable to contact either Huskins or her family members and they do not know where she is.
Huskins' boyfriend had told police Monday that intruders had abducted her from their San Francisco Bay area home and held her for ransom.
She showed up unharmed outside her father's apartment in Huntington Beach on Wednesday morning.
Her father, Mike Huskins, travelled to Northern California to help with the search. Around 9:30 a.m. Wednesday, he said she called him to say she had been dropped off at her mother's Huntington Beach house, about 400 miles from where she was last seen.
No one was home, so she told him she walked the 12 blocks to his home near the beach.
"She wasn't crying at all. She just said, 'Daddy, I'm OK,' " an emotional Huskins told The Associated Press.
Reina Yorba, 12, said she and her mother, Anissa, heard the woman pounding loudly on her father's door in their apartment complex. Then they saw her borrow a cellphone from a neighbour.
"When she was talking, it was panicky. It was loud and panicky," Reina said. She added officers arrived within minutes.
Huskins' return capped a bizarre ordeal that began when her boyfriend, Aaron Quinn, told police she was forcefully taken in the middle of the night from their Mare Island home in Vallejo. Quinn called police at about 2 p.m. Monday to report she had been abducted.
It's unclear why Quinn, 30, took so long to alert authorities, but he is not considered a suspect. Park described him as a witness and a victim.
A car registered to Quinn was taken from the couple's home and found at an undisclosed location, investigators said.
Police said if there is any evidence that Denise Huskins or Quinn committed a crime, they will pursue charges against them.
On Tuesday, the San Francisco Chronicle received an email from an anonymous person claiming to be holding the 29-year-old woman. The person wrote that she would be returned safely Wednesday, the newspaper reported.
"We will send a link to her location after she has been dropped off. She will be in good health and safe while she waits," the email read. "Any advance on us or our associates will create a dangerous situation for Denise. Wait until she is recovered and then proceed how you will. We will be ready."
The email included an audio file of a woman identifying herself as Denise Huskins, who mentioned Tuesday's airliner crash in the French Alps to verify she was alive. Mike Huskins confirmed the voice in the file was his daughter's, the Chronicle reported.
Before police began calling the kidnapping into question, Huskins' father told the AP he knew nothing about a ransom.
"No ransom was ever discussed with me. But police aren't telling me everything that they heard," he said. "It's going to take a while before it all sorts out, I think."
For now, he said, he's just happy to know his daughter is safe. He said he had no doubt she was kidnapped.
"I feel very relieved. Can you imagine? You can't unless you've experienced it," he said. "I don't recommend this experience for anybody."
Denise Huskins works as a physical therapist at Kaiser Permanente Medical Center in Vallejo. She moved to the area in June from Southern California.
Her uncle, Jeff Kane, described her as a person of sterling character, saying she is career-oriented, independent and strong. "She's a good girl, not into any bad things," he said.
Associated Press writers Ellen Knickmeyer in Vallejo and Scott Smith in Fresno, as well as AP researcher Jennifer Farrar in New York, contributed to this story.