One day, you wake up finding out that a person you cared about seemingly vanished, and there are no traces of them; Would you trust your memories, or would you think you are hallucinating?

Like you get transported into an alternate universe where everything is almost same, but with tiny differences. The world looks normal to everyone and you're the only one that have memories of the differences.

Do you think you would trust your memories or would you think you lost your mind?