Found by me
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If you talk to the guard on the left side right before entering the bank in Ironforge(May work with different or all guards) and ask for Profession Trainers, then Alchemy Trainer, at the bottom, he might say:
"::sigh:: ...why o' why didn't I take the blue potion."
You might have to talk to him a couple of times.
P.S. Thanks Ninjanisse