There should be other ways to obtain the Field notes.

[Greydor]

I've submitted a bug report to have them at least check if the drop rates are working as intended. The notes aren't impossible to obtain, but there's multiple components to even having a chance at getting the card, and those are time-locked and add to the difficulty. Considering notes are, for the most part, novelty content (unlike relics in the past which have a BiS factor), the drop rates seem to not be working as intended (but we'll find out!).

Certain notes are more difficult to obtain than atma (pre-nerf, ~2013) based on the limited opportunities to even have a chance for the note.

https://forum.square-enix.com/ffxiv/...ng-As-Intended