Simon Parkes told his family the date he was due to arrive back in Portsmouth onboard the aircraft carrier HMS Illustrious at the end of his maiden voyage.
Allan Grimson, who gained the moniker for his large forehead and hulking 6ft 2in frame, is serving a life sentence for battering two young Royal Navy recruits to death.
Royal Navy Rating Simon Parkes, 18, from Bristol, was last seen in December 1986, when the ship he was serving on, HMS Illustrious, was docked in Gibraltar.