He still has interviews with reporters you god damned idiots! He shows up on state news, talking about stuff. Current stuff. A lack of "public appearances" doesn't mean no one sees him.
Plus, he's not actually in power any more. He's a retired government official. He's a dictator that won the game, he left power while he was still alive and had a popularity that was very high. If he died, the state would give him a huge state funeral.
Cuba doesn't have weird crazy subterfuge shenanigans. That's us. They stay in power by having periodic meetings all over the country so that they can adjust their platform such that they always get more "yes" votes than "no" and don't lose power. Since it's a single party system and your only votes are Yes and No, that's literally all they have to do. They don't fucking bother with having exploding cigars and poisonous shells.
They have the life and death of Castro accounted for. They have something beneficial to do in either case. But the fact that Castro doesn't get air time on US news doesn't mean that he's dead.