I take care of the feral cats to. I havent seen a black one for a week, that has come around for years. Im pretty sure the neighbor did, or had something done with it. Still sad when I go to feed it, and it isnt there. The cat it hung with looks for it to, hesitates to eat, but finally does. I have found it takes two generations to get the ferral out of the cat. It it rare that a kitten taken in, at least for me, doesnt run away in the spring.
Luckily, in gainesville, there are two places, that if you trap the cats, will fix and vaccinate them. They just ask you let them out where you trapped them, they say they try to get back to where the came from, and that usually doesnt end up good. They want them right back in their territory.