Per Tseric on the Profession forums:
We have been working on the resolution of a serious exploit in game which has led to certain consequences that we wanted everyone to be aware of. A hot fix has been recently applied to the alchemy profession, with regards to discoveries. For the time being, we have disabled all chance of a discovery, until we can implement the proper fix through a patch , as we can not resolve this matter solely with hot fixes. We apologize for the necessary but temporary removal of discoveries, and are working to have them re-implemented with an upcoming content patch.
While disheartening for the moment, at least it is only a temporary removal and not a permanent one. I'm sad to hear that my Druid will have to wait for some discoveries (she was so close, too!) but I'm certain Blizzard will get this remedied. It's just a question of if we'll see the alchemy discovery fix patch prior to, with, or after the 2.1 patch. That is, considering the focus on everything going on in the PTRs at the moment...
[image via Mario Caruso]