Annasmom, since we think GW knew what happened to Anna, have you thought that maybe when he died that his social security benifits would go to her? She would have been only 14 years old at the time of his death and if she was with someone whom he had arranged to take care of her they would have applied for his benifits to go to her.
Have you thought of hiring an attorney to check into it? He could petition the courts and get a court order directing the social security office to release anything pretaining to his social security benefits as to whom it was paid out to and the address... This would also work if he had her name changed. Just a thought, but might be worth looking into..........