We have a lot of threads that pop up here about ancient alien and long lost ancient civilization conspiracies as there seem to be something of an obsession around that.
What I find more interesting tho, is the question how much of the modern history (past maybe 2500 years) will be remembered 2 or 5 thousand years down the road.
One of my favorite book series growing up was Frank Herbert's Dune. Dune is set at some indeterminate point in the future by which most of what we consider modern history is largely forgotten or is spoken of and understood much the way we speak of the Trojan War today, mostly myths and conjucture and few reliable sources.
Recently I got into Warframe again, another game which is seemingly set so far in the future that there aren't even passing mentions to anything we consider modern history.
Considering how increasingly almost all the information we record and generate is stored digitally much could be lost either due to storage format obsolescence or due to things like cyber warfare, data corruption etc.
Not to mention the problem of the reliability of sources. What if the only things that would accidentally be preserved about an event would come from sources like Breitbart and Info Wars?
What will be remembered about the Holocaust or the Cold War in thousand years?