So, I noticed when clicking through recipes rather mindlessly, just clicking "use" without paying much attention, that I wasn't getting any "you can't do that" sort of messages; I did get "You have updated this recipe fully" and "you can only use this recipe once" but that was it. And so to prove the bug I suspected was going on, I used Blueprints: Military Academy (Lvl 1) knowing I already had built that building, and sure enough I was informed the recipe had been updated and the blueprints disappeared. I'm assuming this is a bug and not just a "maybe you some pay some attention" thing(although I probably should pay attention and clearly am now). I'm using Mozilla Firefox with Windows 8, and I can reliably recreate this bug.

This is actually not a bug. You can upgrade a recipe in your library. This will reduce the silver price to build it. It does not affect any of the other resources, so it's a questionable benefit, but that's the reason why you can use more schemes and blueprints even after you already learned the recipe. 

After the 5th (I believe) added recipe, the silver price will be half of what it originally was and the game will give you the You have updated this recipe fully message when you try to add another.

Even recipes I've already completed? Say, schematics for a building I've already built in which case the item just disappears if used? Because that's what I have happening. I'm actually aware of the ability to upgrade recipes--it just seems very much a bug when I'm not so much upgrading a recipe as giving my imaginary builder schematics so he can go "oooh we could've done it for cheaper" and he has a hind-sight-is-twenty-twenty break down but otherwise literally nothing happens.