All direct evidence sufficient to prove the existence of super-ancient civilizations cannot be found; at least at his current stage, he hasn't found any clues that could prove his hypothesis correct. The clues he unearthed, from an outsider's perspective, are nothing more than traces of catching wind and catching shadows. Trying to fit them with his theory can only be described as far-fetched and even makes people suspect that he might be marking the target after shooting the arrow.
Only he knows this is not the case. Even before discovering these clues, he had already predicted what kind of clues might be unearthed next based on his theory.
