That is what happened.

He went mad." Joanne's breath was coming brokenly through her lips.

Unconsciously she had clasped her fingers about the hand Aldous rested on her pommel.
"How long he remained in the cave with his dead, MacDonald has never been able to say," he resumed.
"He doesn't know whether he buried his wife or left her lying on the sand floor of the cave.

He doesn't know how he got out of the mountains.

But he did, and his mind came back.