Sorry to hear about it, but reading ur words , it seems he is denied becz didn't appear on interview, its not uncommon, as many ppl are in same boat in either reason of not to be appear/response FP/RFE/Interview. because they never get any letter.
Tell him he is all fine, its little headache but his case would be reconsidered once they get reason.
Procedure: File MTR (Motion To Reopen) discuss with his attorney about it. and not to be worry too much. its common know, there are many victims of that kind of situation. no one know who is in fault.
Use search button on this fourm and type "MTR" u would learn more about it.
Best.
