The Truesilver Breastplate is learned from a trainer, but it's from the armorsmith series of quests. You need to do these quests to get it.
I think almost all end-game recipes will be either from dropped recipes or from trainers who require you to get high reputation with their faction first. It's been this way with Alchemy and Tailoring for me; should be similar for Blacksmithing, I think ^_^