Officers were searching the area and saw a female passenger resembling Valencia in the front seat of a vehicle. The girl reportedly looked at the officers and then quickly ducked down, trying to conceal herself.
The officers stopped the vehicle and determined that it was Valencia. She and the driver of the vehicle, a 20-year-old male, were brought to Mission Station for questioning.
Police said Valencia appeared to be well and will be reunited with her family sometime Wednesday night.
It was unknown if the driver will face any charges.
Valencia disappeared around 6:30 p.m. Saturday from a friend's birthday party on the 13800 block of Polk Street in Sylmar.
Police said she may have met an unknown male on MySpace and left to meet up with him. They said there was no connection between Valencia's disappearance and a shooting that occurred around 9:30 p.m. outside the party, injuring six people, including two children.