Having been adopted myself, by my maternal grandparents, I know firsthand how it feels to not know my birth father. I've been told that I did meet him once, when I was about Four, but I have no recollection of that. My (adopted) parents and my adopted sister have both told me that my birth father basically abandoned me, and during my growth years I never heard from him. I did make contact with him a couple of times by phone when I was in my Forties, but never met with him in person. We lived on opposite ends of the country, last I knew he lived in Washington State, and I had moved from New York State to Virginia, and now I live in Texas. He passed away quite a number of years ago.
Even though I never really knew them, my Paternal Grandparents always sent me Birthday and Christmas Cards throughout my school years, and when I was in my late Twenties or my early Thirties, I did visit them once. They are long gone today.