Carter was last seen in Santa Monica, California on June 28, 2010. After dropping his wife off at the YMCA, he went home and wrote her a note saying he was going hiking and would be back later that day. She called the police after he didn't come home. Carter disappeared hiking near Castaic Lake. His 1979 Honda Civic was found parked near Lake Hughes Road in Warm Springs. He had gotten lost once before, in 2007, while hiking in Malibu, California. An extensive search of the Castaic Lake area turned up no sign of him.

Carter's wife believes he was suffering from mental illness or Alzheimer's Disease at the time of his disappearance. His mother had been institutionalized for mental illness much of her life, and Carter's wife said his behavior changed markedly before he went missing. He spent a lot of time alone, became very distant from his wife and was often verbally abusive to her. She believes he is deceased, in part because he hasn't used any of their credit cards since he vanished.

Carter was born in Cincinnati, Ohio. His father died when he was a toddler and his mother was unable to care for him, so he grew up in an orphanage. He never finished high school and worked as a mechanic, glass-blower and machinist for much of his life. He was a committed Communist and enjoyed writing fiction. His wife stated he collected many things, including rocks he picked up during his frequent hikes. His case remains unsolved.