st_ratagem

"You're right," he says. That he's utterly confident of. There were plenty of times where Loki was utterly infuriating, but nothing Loki had done would ever be enough for him to cast him into an abyss. "If I thought there was even the slightest possibility you were still alive, I would have gone to find you."

Thor believed he was dead, and Odin, pragmatic as he was, gave him no reason to believe his brother may have survived it.