Unfortunately, the optimistic view that "classical civilization" handed down certain fundamental works that managed to include the knowledge contained in the lost writings has proved groundless. In fact, in the face of a general regression in the level of civilization, it's never the best works that will be saved through an automatic process of natural selection.
Lucio Russo, Silvio (translator) Levy (2013). “The Forgotten Revolution: How Science Was Born in 300 BC and Why it Had to Be Reborn”, p.8, Springer Science & Business Media