David was last seen at Embudo Hospital on January 10, 1970 in rural Dixon, New Mexico. He was with his mother's boyfriend, Zerfas, at the time. His mother, Genevieve Miera, was hospitalized overnight the day David disappeared. She last saw David and Zerfas outside the hospital. The pair may have left on foot, hitchhiked or rode in a faded green 1946 Chevrolet Pickup truck.

Genevieve was released from the hospital a day or two later and came home. She, David and Zerfas lived five or six miles from the hospital, east of Dixon, in an area known as the Canoncito. When Genevieve arrived home, David and all his belongings were gone. Zerfas claimed the baby had been given to a family in Santa Fe, New Mexico. He later said the family moved to Mexico. His story has never been verified and David has never been located.

Genevieve alleged that Zerfas abused her and her child, and David's disappearance is considered suspicious. Both Genevieve and Zerfas are now deceased. David's disappearance remains unsolved.