A recap of D.B. Cooper's 1971 airline hijacking and extortion, and his subsequent disappearance after parachuting out of the plane over Washington State; new forensic evidence suggesting murder in the 1987 deaths of two teenage boys on a Bryant, Ark., railroad track; a story on missing memorabilia acquired by a Medford, Ore., sports collector, who died in Las Vegas in 1987; and an update on a previous report on a prison escapee.