[fsloth]

"But how did we manage to lose the knowledge behind the Antikythera device and why was it not recorded?"

The idea that one should share ones inventions is not universal. While other wrote profusely, other ancient sages often guarded their discoveries fairly jealously.

I'm pretty sure lot of pre-20th century discoveries have been discovered several times by various people, but the surrounding society has not benefitted from their knowledge for various reasons.

An excellent example is Leonardo da Vinci. If this question irks you, I warmly suggest you read Isaacson's biography of him.

Leonardo discovered several scientific principles hundreds of years before his time, including Newton's third law, and the fluid dynamic operation of the human hearts aortic valve.

But since he never published anything, references to these were dug out only by latter day historians, and did not benefit his contemporaries.