A 9-year-old girl who disappeared from her family's California campsite was found alive 21 hours later Saturday by a pair of mountain bikers two miles away, the Marin County sheriff's department said.

Ida Rothschild of Santa Fe, New Mexico, vanished about noon Friday from the campsite in Samuel P. Taylor State Park, the San Francisco Chronicle reported. She was found about 9 a.m. by two women riding along the Cross-Marin Trail and reunited with her family, deputies said.

"She told them she'd been lost all night long and that she never stopped to sleep. She'd just been hiking all night long," Marin County Sheriff's Lt. Doug Pittman said.

The girl was found just outside the park's boundary, the Marin Independent Journal reported.