I am sorry for your loss. This whole situation is shocking. The victims weren't doing anything wrong. I am sure you feel a bit of "survivor's guilt". I couldn't imagine losing an animal this way.
However, you may want to be more active to prevent or justify your loss. I would suggest contacting the company if you haven't already. Also, make sure your vet has any proof/samples possibly needed. Do you still have any of that food leftover? You may need this for "evidence".
I have not heard anything about the Diamond Dog food's committment for compensating or dealing with anyone who has lost their pet due to this tragedy. The last I heard there were atleast over 20 dog deaths associated with this. That will possibly mean a class action lawsuit for you to pursue.
I wish you the best of luck. Please adopt again as we do need more happy homes for our animals.
By the way... Cool screen name! I have a Scooby and Shaggy myself!