Can confirm still broken. Wish bungie did a PSA on launch of the game for people with the mission enabled or something. Just lost the black armory key when using it thinking it was fixed in last weeks patch.
That would genuinely solve the problem for most people. I, like you, used my key as soon as I obtained it once last week's fix went live as they said it was fixed. Like it sucks that it's broken in the first place, but not posting a message to raise awareness of it being broken is ridiculous and somewhat cowardly from Bungie. All it would take is a message like the "next week in destiny" ones that pop up every now and then saying "DO NOT USE KEYS/CRYSTAL - IZANAGI'S BROKEN AGAIN". If I saw that, I'd be annoyed I couldn't progress, but at least I wouldn't have to go and regrind the key mold again (which it looks like we'll have to do, assuming they can even fix it so we can obtain the key-mold again). I'm not expecting or even asking for a bug-free game, just for the people making it to front up to their mistakes and minimise the damage to players, even if it means admitting on the title screen that they screwed up.