It was not your imagination.
You tried to keep the baby bird alive, but nature took hold more quickly than you could find food. It was just one of your many mistakes in trying to take care of the baby bird. You also put a rock on it to keep it warm. Then you tried to sit on it to keep it warm. You made several poor decisions, none of them quite as terrible as just removing your undivided attention from the baby bird. It needed you to watch over it at all times, but that is where you truly faltered as a guardian.
You tried, however, and that is a pretty nice gesture. Would you like to try again?