I always thought that the "what happened to the rest of the crew " line was insanely creepy, especially since shortly after that Lambert says 'lets get the hell out of here". When you watch it for the first time, you know as much as the crew. The idea of an abandoned ship with no signs of the rest of the crew is just spine tingling. I always assumed that the line was an implication that something bad happened to the others and that its a premonition about what will happen to the Nostromo crew. So I believe there were others, but they were killed by alien/aliens. Perhaps the jockey was the "Kane" of the crew