Thirteen people have gone. - They have gone home or something like that. It's just the past perfect of go.
Thirteen people are gone. - They have been abducted by aliens, or fell overboard at sea. To be gone is to have disappeared or at least to have perished somehow.
I'm only a low-level Swedish learner, but I have mapped bort in my head to a Klingon verb meaning be all gone so I think that bort is not equivalent to a past perfect of gor or oker (those o's should be a's with rings, but I don't know how to get the right letters on my US keyboard).