Authorities are hunting for the alleged kidnappers, who Papini said dropped her off 150 miles from her home on Thanksgiving Day.
"I saw a woman with long blond hair by the side of the road kind of frantically waving what looked like a shirt," the driver, Alison Sutton, told ABC News. "I figured if she was willing to risk being hit by a car, she must really need help."
Sutton said she spotted Papini early in the morning of Nov. 24 and called police.
Papini, 34, who had reportedly been held captive for three weeks, was able to flag down help even though she was bound with restraints.
She told authorities her captors were two Hispanic women armed with a handgun and driving a dark-colored SUV.
Investigators are analyzing the restraints and Papini's clothing for DNA evidence as well as surveillance video in the city of Redding and in Yolo County.
The Shasta County sheriff told ABC News that she will be interviewed again this week.
Editor's note: An earlier version of this story gave an incorrect name for the county where investigators will continue analyzing surveillance video. It is Yolo County.