Wow, dude, sucks. I put my dog down when he turned 17, I had him since I was 9, and that was tough. They're like little people, and frequently they become as much members of a family as the humans are. It was tough for me, it's still tough to think about it. Animals deserve our love and compassion though, and you should be glad he had a nice home. Animals don't understand us as we do each other, but as long as you showed love and affection towards him, he was certainly happy for the time he spent with you.