Oh Mary, I am just seeing this thread now and I am so saddened by the outcome. Buddy was such an adorable cat.
Please don't second guess what you think might have happened to him, as you know cats with Feline Leukemia, look very healthy and can live for years with this disease. Personally, I agree with the others that say you made the right choice for him.

Kimlovescats said it best: " Try to find comfort in knowing that you prevented him from ever knowing the suffering of his illness. He came inside, loved you and yours, then went to sleep! No pain, no suffering!"

{{{{{{HUGS}}}}}}