It seems that there are different realities and different levels of life and death. For example, if Sun had stayed on the Island, she would have died since she was pregnant, so maybe on some level that happened; and Jin survives on the Island without her. I don't believe Lock is really dead either, not on the Island. Did you notice the name on the coffin? It made me wonder if it was really Ben body, that looked like Lock
So confusing. I wish they had shared more of the "secrets," but just as long as the keep on showing Sawyer, I'll be a fan.