Icecrown: Gear sets are gone after maintance?

Hi, can we get a little information on why or how gear sets created by standard blizzard feature got removed after maintance (or some time around that)?
At first I thought it was a client problem or even a security issue (which seemed strange since I have 2FA and no one has my accounts info), but after closing and re-opening the client and trying multiple character and asking around, everyone's response was the same, they lost sets created that way :(
I tried to search forum or main page, couldn't find an answer there