You're NOT a failure! The store is the one that lets these guys down, sometimes we can't save them all, but at least you stepped up to the plate and TRIED! You gave him warm, clean water, and all of the love that he needed, and I'm sure he passed on, feeling comfortable for the first time in his life.
You gave him so much in just the short time that he was with you, and you should be proud of your efforts. Not many people do what you do, you're a hero, and an advocate that these guys so desperately need! -big hugs-