King County Sheriff’s Office spokesman Ryan Abbott said it was a “miracle” that 18-year-old Giovanna Fuda was discovered after a week-long search on Saturday.
Mr Abbott said she probably survived by drinking water from a stream, but did not have food with her and he was not sure what she was eating.
“She is in stable condition,” Abbott said. “It’s a remarkable ending. ”
Ms Fuda was last seen on July 24 when she left her home in the Seattle suburb of Maple Valley without telling her parents where she was going.
His car was found abandoned the following night near a mountain pass about two hours northeast of Maple Valley.
“We don’t know why she was up there,” her father, Bob Fuda, told NBC affiliate KING-TV.
Authorities said the car, a 2008 Toyota Corolla, was out of gas.
Her purse was still in the vehicle but her cell phone was missing. The King County Sheriff’s Office initially called her disappearance “suspicious.”
Mr Abbott said the area was a dead zone for cell phone service, so it was difficult to track his location via his phone’s GPS.
A dense brush also made it impossible to search with a helicopter, he said.
After a bloodhound found his scent more than a mile down the highway on Saturday, a search and rescue team ascending a ravine and following a stream found his notebook, shoes and clothes, said Mr. Abbott.
They eventually found her too, a few kilometers from her car, he added.
She was alert and conscious but inconsistent.
“We don’t know how she got up in that area,” Abbott said, adding that she may have turned around while walking to get gas.