Oh my God, that is horrible. We've had some nasty, NASTY crap come from the grooming department (maggots falling out of mats, having to sheep shear an OES, a solid mat of feces covering the total stomach of a cat, etc.), but we have never had a dog that bad. I'm so glad he was able to get help!
And hoorah for the groomer. I don't think I could have stomached working on a dog with cockroaches crawling out of it. *shudders*