For the past week I've been grinding Dungeoneering floors for a few hours each day trying to get this drop (it's the last journal I need and I don't care about getting any actual dg levels anymore, so I decided why not).  Wikia says that it should drop from monsters and bosses every 6 floors (that would put it at floors 25-30), an older RSOF thread said every 4 or low Furnished floors (so that would be 17-20; I didn't add these to my rotation until a few days ago).  To make it faster, two days ago I started C1'ing the floors, but still no luck.  My fear is that I'm doing the wrong floors (given the varying information) and wasting a ton of time.

 

If someone happens to remember the specific floor they got it on I would love that information so I can grind that single floor over and over with confidence that it'll eventually drop.

 

EDIT: For any future people that stumble upon this... I gave up after a few more hours.  I feel like the most unlucky person in the world and didn't want to spend another 100 hours (yes, I literally wasted this much time just trying to get this one page) without the guarantee of getting the drop.  I wish you better luck than I had....

I seem to remember on Frozen floors for myself (not sure which one, sorry :/).  I'd just run 1-35 normally until you get it and try not to stress too much :) in the meantime.

Got mine during floor 24.