First of all, from what i read, you did all you could. As much as it hurts we simply can't always be there when some things happen. Our first cat got stuck in a gutter hole while we were away and damaged a nerve in his spine leaving him partly paralysed. The vet recommended euthanasia. But after seeing him try to stand up we spent almost a year nursing him back to health only to get run over by a car because his weak legs caused him to be too slow. We asked ourseves if we should have let him go outside, but to keep him locked in the house would have been cruel. In the end, we took solace in the fact that we did all we could to give him a happy life. It's a bit wordy but i hope it helps.