Eh, I'm not sure as much is truly lost as one might currently think.

There's a number of things that seem more like an issue of history as a field having challenges in undue influence of academic popularity contests and subspecialty isolation.

For example, the face of the historical basis for Helen of Troy has likely been on modern magazine covers, we just haven't broadly realized it because most modern historians throw out Herodotus wholesale so they've ignored the details in his version of the Helen narrative, which happens to connect the events to part of Egypt's history that's been similarly poorly evaluated by scholarship to date.

Even the way Homer and the Trojan War narrative gets handled is pretty ass backwards, with scholars preferring to just hand wave it as mythological history rather than seeing it as having combined a history of the Mycenaean conquest of Anatolia in the LBA with a later sea peoples capture of Wilusa back from the Hittites in the EIA (it has rather impressive levels of detail around events tied to both these things).

We see modern debates about whether the Exodus narrative occurred or not as described in the Bible but there's very little investigation into the Greek and Egyptian accounts of the same which differ significantly from the Biblical version (notably about it being ethnocentric), even claiming the latter version was altered. Versions that might be quite relevant to recent archeological finds like the Aegean style pottery with local clay in Tel Dan or the imported bees from Anatolia in Tel Rehov.

Give it time. A lot of big topics that are generally dismissed or thought to be lost today might not still seem that way within a generation or two.