Their "vetting" was just to make sure they could show that they didn't know that the claims were false.
They didn't, and don't have to, "vet" that the claims are true.
I haven't read the story, but I'm sure it reads: "the maid says... the maid claims..." etc.
Well, remember, the 'maid says' claims were enough to successfully prosecute the distributor, who was the actual focus of this investigation. I think Rush will be considered by prosecutors to be 'just another user'.