This isn't an ideal answer, but for what it's worth, I didn't need either the knife or the clue that was in the drawer to finish the game. The clue wasn't directly used in solving any mandate, it wasn't needed in any conversations to obtain other clues, and the knife was only used one time (on that drawer).
So, if you feel like you're stalled because of the knife, you could just go on playing. You'll basically just be missing a piece of "window dressing" that adds to the atmosphere of the game but isn't necessary for solving the mystery.