She was suspected of traveling with a man named Dave Burton Egert in a 1994 Toyota T-100 pickup truck, with a California license plate 4X02600. The teen reportedly met Burton online.
U.S. federal marshals took Egert into custody Monday afternoon. He was found alone and detained in Altadena Monday.
Bradford is described as a black female, 5 feet 7 inches tall, weighing about 105 pounds, with brown eyes and black hair. The OC Sheriff's Dept. classified Bradford as a "runaway juvenile."
Investigators allege that Egert used MySpace and Facebook to send the girl sexually explicit information.
Authorities have not said where Egert lives.
If you have information on the case, you're asked to call the Orange County Sheriff's Department Special Victims Unit at (714) 647-7419.
The Associated Press contributed to this report.