I'm so sorry for your loss, i just had my cat put to sleep and i'm so sad too, i really feel for you. I lost a cat on the road 3 years ago and i didn't see her, someone found her and she got taken to the vets, i just thought she was missing untill i asked down the road. It really is hard but it will get easier. I keep telling myself that and that i done the right thing with my gorgoeus Leo yesterday but we will just keep kicking ourselves and telling ourselves that we could of done things differently but just try to think of all the happy times and how happy your cat was when it was alive and that you gave it a good life.