Hey there!

You're right that it's not a commonly accepted theory, and for good reason. There's no evidence. Most arguments for it are based on "We don't know anything about this era.. So it could be?" This mentality hardly lends itself to any kind of scholarly research, which is based on making conclusions from observations. While I can recommend some good books in why the "lost ancient super-civ" trope is so prevalent in the West, or on what excavations reveal about the earth during the era of these hypothetical civs, if you would like, but I have never seen a book with anything resembling a scientific approach that takes ancient advanced civs seriously.