Covered in burns and bruises, Autumn hiked out of the rugged North Cascades Mountains two days after Saturday's crash, police said.
She flagged down a passing motorist, who drove her to a store in Mazama, Washington, near the Canadian border. The man called police before handing Autumn the phone.
"So tell me exactly what happened," the dispatcher told the girl, according to a transcript of the call.
"I was riding from Kalispell, Montana, to Bellingham, Washington, and ... well, I don't know where, but we crashed and I was the only one that made it out," Autumn said calmly and in a low voice.
"Made it out from the collision?"
"From the plane," she said.
"Yeah, the only one that survived."
"Are you injured at all?"
"Yeah, I have a lot of burns on my hands, and I'm ... kind of covered in bruises and scratches and stuff."
Autumn was flying with her grandparents, Leland and Sharon Bowman, in a small private plane when it apparently ran into trouble.
Jessica Jerwa, a spokeswoman for the Washington Wing of the Civil Air Patrol, told CNN she called Autumn's father, David, with news of her survival.
"It was incredible for me to be able to give that information," she said. "I have a 16-year-old son myself."
David Veatch had been napping at the time.
"He was still a little sleepy when I told him that Autumn walked out and that she was safe," Jerwa recalled. "He just sort of paused and took a moment, and then just went, 'What?'"
Autumn's friend Chelsey Clark said the girl slept part of the day but seemed to be in good condition. Autumn left the hospital late Tuesday, hospital spokeswoman Melanie Neddo said.
"It is a miracle what happened. We never gave up hope and we just felt like she was still with us," Clark said. "It's absolutely amazing to see her in good spirits."
But Autumn is struggling with the loss, Veatch told CNN affiliate KCPQ.
"These people were really playing the part of grandparents to her and that's hitting her really hard," he said.
He added, "I believe in God. ... There's no way I cannot believe in God."
The 1949 Beech A35 aircraft, registered to Leland Bowman, dropped off the radar near Omak, Washington, just before 3:30 p.m. Saturday, according to authorities. It had taken off from western Montana around 1 p.m.
Hiking for help in cold wilderness
"Autumn did not tell us the condition of her grandparents, but it doesn't sound good. It doesn't sound like they made it," Okanogan County Sheriff Frank Rogers told CNN.
He recounted the teen's story of survival.
"Autumn said they flew out of the clouds, and then flew into the side of a mountain. She was able to get out," Rogers said.
The girl found a creek and followed it.
"At first she was nervous, she said, and she was scared," the sheriff told CNN's "Erin Burnett OutFront. "She followed it all the way for two days, spending the night along the river there once."
She eventually found a highway, where she was rescued.
The girl was taken to Three Rivers Hospital in Brewster, the sheriff said. He told CNN affiliate KCPQ that Autumn's survival was miraculous.
"It gets cold up there at night, pretty high elevations, so she survived not only the crash, then going through that. I will just tell you this from all of us here -- we are just impressed with her, she's like a kind of superhero."
Veatch told reporters outside the hospital that his daughter was "pretty banged up" but doing OK.
"She's just an amazing kid," he said, according to CNN affiliate KOMO.
Autumn developed rhabdomyolysis, a muscle disorder, during her ordeal, but suffered no life-threatening injuries, said Scott Graham, chief executive of Three Rivers Hospital. Rhabdomyolysis is often caused by an injury that damages skeletal muscle, according to the National Library of Medicine. Fibers from the damaged muscle enter the bloodstream and can cause kidney damage, but recovery is possible with treatment.
"Autumn's doing very well. She was severely dehydrated, had some minor burns, abrasions, several lacerations that were all taken care of and are healing well," said James Wallace, a doctor who treated the girl. "She's extremely exhausted and will remain pretty spent for the next couple of days."
Veatch told the Bellingham Herald that his daughter tried to help her grandparents out of the plane but couldn't. She waited for rescuers near the crash site for about a day, crying, the newspaper quoted him as saying.
Rogers, the sheriff, told CNN that Autumn reached into the aircraft and tried to grab her grandparents to pull them out. That's how she got burned, he said. The plane was on fire.
The girl drank from a creek, but not too much because she was afraid of getting sick, the sheriff said.
Crews are still looking for the plane and the girl's grandparents. The mountainous terrain is complicating the search, but information from Autumn may help first responders find the crash site.
Lt. Col. Jeffrey Lustick of the Civil Air Patrol told KCPQ the searchers were "overjoyed" when they learned Autumn had survived.
"It's a miracle when you have a plane crash of this type," he said. "It's a rarity to have someone come out of this and be able to walk out of a crash scene."