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?
This is the movie Yesterday, where a failed musician gets knocked out and wakes up in a world where the Beatles never existed. A few other things too, but mainly the Beatles. Spoiler: he becomes a mega star.