Plastic?
I wouldn't be surprised. There was a steady accumulation of knowledge for a thousand years or more and then in the third century civilisation nearly ended in Europe, North Africa and the near east due to natural disasters, war and economic collapse. Books couldn't be recopied due to lack of funds and later rising religious extremism saw book burning and the murder of academics. By the dark ages, barely anybody could read.
The monks who copied what was left? They were mostly illiterate! Just copying meaningless symbols with perhaps an abbot who could read in at least one language overseeing. That's why there are so many drawings and decorations, really. They were bored!
A thousand years of advancement swept away and everything starting again from savagery. The Romans had central heating, advanced roads, they knew the world was round and about dinosaurs. Ancient engineering is the stuff of legend. They had planetariums of a sort via stage magic and sci-fi novels about intergalactic wars.
Plastic wouldn't surprise me at all.
