I can't seem to find any info on this, but I'm sure there was a special note in the Chancel east room that becomes unobtainable after a certain point. What's the deal with this?
The note talking about Johann Weyer's recipe? After you've collected all the orb pieces and get imprisoned, the Shadow blocks off access to it. I don't remember if it's perhaps possible to find that same note elsewhere after that point (in case you didn't pick it up), because all the ingredients are obtainable in alternate locations after that.
So I imagine the only way to get it is to head straight to the Chancel first after arriving at the Nave?
I mix these rooms up a bit. The Chancel is the big cross? Or where you find Agrippa? I was thinking the area where you find Agrippa, by the entrance to the Choir. If you mean the bridge that collapses in the big cross shaped room, then I believe it only contains some story bits that aren't vital for progressing.
The Chancel is the big cross yeah. The Nave is where Agippa is. Anyhow, I managed to pick up that note by heading straight to the Chancel after arriving at the Nave. I had to slip past a Grunt but that wasn't too hard. I originally wondered because of the new achievements that are coming and there's one for collecting all notes.