[She'll riffle through the letters then, seeing if there's something important. Naturally she's reminded of the letter she's written in the event of her death, so who knows? Maybe Clyde did something similar.]

If the knife and letter opener are missing and the drawer was locked when we found it, chances are they could have been used to kill Clyde. I would think if they aren't in his drawer then they would be on his person - his card did mention being useful with "improvised" weapons.