This is a very difficult one and I wish I could help you. If the National Archives in Norway have already checked to see if he was on another ship, and have come up with nothing, it's possible perhaps that he joined an American ship or one of another Nationality? Have you ever tried writing to American Archival institutions, or British ones? It could also be that he decided to take a job on shore, and ended up settling in America, in which case he should also be listed in various archives. If he died in America (or Britain) later on, he would also be listed.

Siri