Even if it is empire justification, there is going to be a ton of actual information in there about the way of life, hierarchy, gods, professions and whatever other incidental thing comes along with the royal honorifics.
Usually destroying a library is a haphazard thing done by illiterate people. When the secularists raided the monastrys during the Bildersturm, the old tomes were used to line the muddy roads, thrown into ditches and ponds. Maybe something similar happened here. One of the helpers, afraid of the return of the empire that always was, packed holy scripture into pockets/pots and then took it home. In that case it would make sense to look for them near the old villages of the tribal helpers?
Destruction of the Mayan codices wasn't done by illiterates out of ignorance, it was a deliberate, systematic policy by Franciscan missionaries to eradicate the Mayan religion by destroying any writing which might support, reference, or communicate it in any way.
