Dylan Redwine was last seen Monday.
The boy lives in Colorado Springs but was visiting his father in La Plata County on Thanksgiving break.
La Plata County Sheriff's Office spokesman Dan Bender says Mark Redwine told investigators that he saw his son Monday about 7:30 a.m. The boy was gone when Redwine returned after running errands.
Elaine Redwine told The Durango Herald that Dylan wouldn't have left willingly and would have called if he were able.
The missing boy is 5 feet tall, 105 pounds, with blond hair, blue eyes and fair complexion. He was last seen wearing a blue-and-white Duke Blue Devils baseball cap, black Nike T-shirt and black Jordan tennis shoes.