For about lost technologies, exist very interest niche, remembered to me by mentioning of Roman concrete.

Example, ancient natural asphalt, which literally surfaced at Red sea.

So, probably natural material, not always exactly known how appear, but fortunately existed and used by ancient people.

I only cannot agree that all lost technologies are not that we might truly care about. As example, Roman concrete could be really valuable in modern world, as current concrete just is being destroyed with time, and this is very serious problem, because could be dangerous for constructions like large dams and bridges; also, need some solution for long term burial of radioactive trash.

How to save such info, very interest question and not easy. Possible example could be some sort of long term independent shelter, under Moon surface, where could store digital archives with information.

Haven't you seen https://en.wikipedia.org/wiki/Moontrap / https://www.imdb.com/title/tt0097911/ ?