Looking for my birth grandmother- adoption occured in Moss Bluff, LA

My mom's bilogical mother was a rape victim or so my mother has been told and put my mother up for adoption. My mother has been lied too all of her life about the adoption. I am getting no where in finding her. We had a strange phone call a few years back from a man who said he was her brother from Pennsylvania which is where my biological grandmother is from. He didn't give a number, his name, or anything. And he never called back. So now I am confused on why. I want to find her and my real family so bad. I have a picture of her and I look like her more than my mother does. Her name is Dorothy Diamond. But the last name is a maiden name. I am sure she is married since I know she has children. All I can hope is that she looks for us.