Yes.

But usually you realise after the fact learning that it was when you could have interacted with it.

Those things exist then through legends and the collective that still remembers, though that collective is very prone to just misremember.

That is a good question and I'm struck in the English language between lost and gone.

If it's just lost I might still find it. I believe the post I'm looking for is lost. I don't know if it's gone. If it's gone I will never find it.

Could be it if it's lost there must be knowledge of it?