Loading Occult Adventures causes the Investigator Talent, Alchemist Discovery, to not load. Steps to reproduce.
1) Load all sources needed to create an Investigator.
-Advanced Class Guide
Advanced Player's Guide
2) Load Occult Adventure also.
3) Proceed to create a character up until level 3 to unlock Investigator Talents.
4) Alchemist Discovery is mission from Investigator Talents.
Repeat all steps except Step 2 to see that the talent comes back.