This is bullcrap! My dad had to put his 8-year-old white Persian to sleep because of kidney failure, probably after eat it some the poisoned food. Needless to say, he does not have his original receipt, or the packaging, or any pictures of the cat while it was wasting away (since neither he nor the vet knew what was happening at the time, at least until the news broke, and everything had been thrown away. Class action is the way to go on this, if for nothing else to drive Menu Foods into bankruptcy, which it and its suppliers richly deserve.
It's more than likely a participant in a Class Action is going to maybe need more documentation, not less...otherwise, it's a toss out of court.
(kinda like those Chicago bus accidents where there are 3 passengers, but 45 witnesses in the 'hood end up claiming bad backs)