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?