Logan-

Something very similar happened to me about six years ago. I was home for lunch on a Tuesday when the exterminator came around (I lived in an apartment at the time, and they sent him around every couple of months). I had two cats at the time, and he was obviously a cat lover, because he had to play with the cats before getting to work (incidentally, I distinctly remember his pet name was for my cats - "butter kitty"!). Then he told me that the people at the other end of my building had moved and left their cat. I was horrified! I was only vaguely acquainted with them - I didn't even know they had a cat, but I knew they had moved because another neighbor, Kelly, who I was close to, had helped them. They had been gone since Sunday. Me and the exterminator made a pact: He would not tell the manager I had another cat if I wouldn't tell the manager he had let me into a locked apartment to get another cat! So we went in, and all she had was a tiny, nearly sandless litter box, with no food, no water, and no fan or air conditioner for three days(this was June in Texas). I took her and within a few days realized she was pregnant. Another friend of mine wanted her, but not until she gave birth.

After the kittens were born but not yet weaned, the woman who had abandoned Misty had come to visit Kelly, and Kelly brought her over to see the kittens. But this woman had it in her mind that she was going to take Misty home! I told her that Misty would have to stay at my house until the kittens were weaned, and at that time she was being adopted. The woman said that she was her cat. I told her that she had abandoned the cat, and that I would never give her over, and that she would have to go to court if she wanted that cat back, and of course I had witnesses to the fact that the cat had been left with no food or water in an 85 degree apartment for three days. She left in a huff but I never saw her again.

I, personally, would not approach the former owners. Of course, if they seek you out you will have to make your own decision, but if it were me they would get about as much sympathy, and as much of a fight, as Misty's owner got out of me. It would be a completely different story if the cat had been well cared for, but like you say, he was not even neutered.