Unanswered question -- spoiler obviously

When the real Sebastian shows up in Denmark and says something about escaping Hanoi as a false corpse, how did he do it? Was the Orpheus thing part of his plan all along?

Great film overall. I hardly ever watch a movie twice and I restarted this one right after it ended. Everything was super tight and well paced. Reminded me of a combo of Vertigo and The Third Man.