SOLVED. Alternate dimension book, about what the world could have been. [s]

[Amanda]

My dad told me about this book, but for the life of me I can't remember the author's name or the title. I remember that the author met a man outside of his hotel room, and he at fist thought the man was the usual crazy people that knocked on his door when he was at a hotel. But then he started to listen to what the man said, about how we're off of the path of what should have happened to make the world a better place.
The man told one story of how the person that was supposed to invent something that had to do with changing gravity was never born because his parents were killed in the Holocaust. The author wrote a book based on this encounter. He tried to find the mysterious man again using all of his resources, but to no avail.

[Lobstergirl, au gratin]

Amanda, are you still looking for this?

[Amanda]

I found it actually - The Key by Whitley Strieber.

[Sophie]

Move to Solved?

[Michele]

The Key: A True Encounter for the clickiness