Architect's Key

[Netatsake]

Is the key a guaranteed spawn? I have searched every wall in the graveyard for runes and opened up 3 of them in my current run with no key showing up. The wiki states it's specifically in the underground area (which I assume is the area opened up by the other key?) but I've checked every wall I can reach above and below ground to no avail.

[kermat_]

It's a guaranteed spawn until you find it, unlock the door and hand in the blueprint behind the door. This is the Merchandise categories blueprint.
Maybe you were just unlucky and missed it. You should check every wall and floor. It shouldn't be possible for the game to skip spawning the key in a wall or a floor, but this game is not without its bugs. I'd say try another run and see if you find it there.