There should be other ways to obtain the Field notes.

[WhiteArchmage]

Field note 1 is dropped from the "More Machine Now Than Man" Skirmish in the South Area of the Bozjan Southern Front.

Funny enough, I got it after 2 hours of trying to get the FATE up and then failing to get it. The only one I'm missing from Southern Front is Sartauvoir, and after 2 MORE hours of spamming all his Fates still hasn't dropped. Annoyingly, I stuck around after Help Wanted to do Pyromancer Supreme, it dropped the Field Note on the latter but Sartauvoir doesn't drop his own Field Note in the Fate that's against him! So the best choice seems to be getting picked for his Duel.