The answer is that he started believing in God more and so he technically got saved because after his father died he had nobody but God so he started to believe little by little all throughout the book. I hope this helps.
At the end of the book, Wiesel describes himself as a corpse when he looks into the mirror. This statement he makes reflects his spiritual attitude because he has completely lost his faith in the humanity, he feels he has lost also his morals. He feels empty as a human being, specially after the war and the extermination of his people. He becomes hopeless.
At first, he has a strong and loyal relationship with God. He was a man of faith and talks about how he reads the Talmud and attends the synagogue. All these happens before the war. After, he completely changes and loses his faith in God, we can see this clearly when he says: "God is hanging on the gallows" during the hang of a young boy in front of the camp.
