Doctors can only respond to information presented clearly. If the grandparent didn't advocate and be clear about the concerns then the doctor would likely miss most things in a short doctor visit. Do you feel confident the information you have observed was presented as needed? I would suspect that at this point in time the grandparent likely still isn't advocating for the child needs.

I wouldn't give up your efforts because the doctor hasn't acknowledge your concerns. You, as one person, can only do much but what you do will make a difference.

As for toilet training I would look for visual pictures to help the child express his needs and for the child to consult for every step of the toileting process. I've used PECS in the past in school/daycare settings but you can likely find all sorts of good pics online to use.