What if some ancient Orwellian 1984-style history filtering system had actually succeeded? We would never know about what exactly it had filtered out. Thus we would never discover any contradiction between its filtered version of history and the real one. The unseen past is unknown, by definition. This is the Unknown Unknown problem of history and archeology.
History filtering has been the standard operating procedure of many ancient civilizations. The Persians appropriately refer to it as “striking out from the book of time”. Archeologists have trouble finding material support even for events that are recorded as witnessed by multiple independent sources. It would not be too difficult to destroy some already scarce historic evidence. Especially in ancient times: just grind a few clay tablets and kill a few dozens literate enemies.
We cannot hear the mute.