I have done this multiple times, never with a happy ending. It's still worth it, to know that they will have softness and care in their final moments.
I'm so sorry. It's very upsetting. But you did a kind and valuable thing.
Thank you for trying.❤️ A cat brought her kittens to live in our side yard and no rescue will take them. So we just do what we can. But it never seems like enough.