> "Oh hey, there's some good books under a mountain in another continent" is going to be pretty low on the list of things that's preserved through oral lore.

I think that knowledge would become the new gold/buried treasure in such a world. They who have the knowledge wins, and it will become potentially far more valuable than any stash of Gold.

If that is true for such a post apocalyptic future, then the lore of the buried treasure in the salt mine will probably spread and many will seek it out.