Yesterday, I got the quest to make Fertilidust Lite, and when I tried I was told I hadn't yet 'discovered' Humbabol and Potoxin (it was true, I hadn't). So, I put my beaker away and dusted off the old test tube, did some 'experimenting' and made some of each. I'm afraid I can't remember if I got the 'Discovered new thing' popup at this point.
Anyway, I then went back to the beaker and tried for the Fertilidust again. It still said that I hadn't discovered Humbabol and Potoxin, although it did correctly identify that I now had enough of each now to make my Fertilidust:
farm6.static.flickr.com/506...
I made my Fertilidust, completed the quest and continued on my merry way.
Checking in again this morning, I see that now, if I go to make Fertilidust, the game is happy that I have indeed dicovered the necessary compounds. I didn't do anything else with my test tube to make it notice this, other than wait a bit.