If the diarrhea continues more than 48 hours even with the bland chicken and rice, it's time to see the vet. Dogs eat gross things and often get sick because of it (poop, garbage, dead animals, etc), but usually this will pass in 48 hours and it will be out of their system. Longer than this is a concern, as you and others have mentioned, of something that will not just pass through on its own, parasites, bacterial infection, virus, and the dog may need treatment from the vet. Also, at this point your dog may be getting dehydrated. I hope by now your pup is on the road to recovery and it was simply a case of dog eats gross things and stomach is paying the price.