Just to be clear, mom is taking him back to the former marital home, but you are living with your folks?
Do you know that he even has a lawyer? Have you formally filed for divorce? If so, his lawyer's name should be on record with the court where your divorce is pending. If there is no lawyer's name on file, then he hasn't formally retained one. I believe that everywhere it's the lawyer's duty to file an entry of appearance when they are retained in connection with a specific pending legal action.