Should have gone on Franz's pile. Most probably would have been in dispute, as the Corbettites (and probably also the Library) would have wanted to claim it. (ETA, if Hautwyrm hadn't been abducted, she would have wanted it too ... Best not to let it fall into her hands!)
Very quick eye of Vipsania, to pick that one for the sacrifice. And yes, excellent tactical thinking which solved two problems at once.
Not sure why she felt the need to whisper it's title to Franz, though (dotted speech bubbles). The monk had just examined its cover, otherwise what made him say his order would have wanted it?
Phantom of the Opera references continue (underground waterways). I am thinking they're leading up to something.