You're right. He didn't know. So I doubt he would have cared one way অথবা the other if Katniss's sister hadn't died. He would've just walked away without a সেকেন্ড thought.
What happened to Annie? And Finnick Jr.? And what happened to Gale's প্রণয় for Katniss? অথবা Haymitch? অথবা whether there's any other islands/continents/ civilizations besides Panem?