Was my maine coon cat neglected?

Hi, I've owned a 4 yr old maine coon for about 3 months that we named Leo. I went to our local shelter and adopted him. What I noticed immediately was that he was very skinny (could see ribcage and spine) and had a "lion cut" at the shelter. It didn't bother me since he was very friendly and had a wonderful personality! I asked the adoption people if he was ever abused or just a runaway but they told me they had no idea since he was just surrendered to them by the owner. I was never instructed that he should have any special medical care (besides taking him to the vet in six months to get his shots b/c they apparently knew of when he had his last shots by the owner) Now that I've had him he is gaining weight and i'm letting his fur grow out....looking very normal now. I've already scheduled a vet visit in 2 weeks and going to ask them as well. I just wanted to ask on here to see what you guys think. I love Leo and he is a very loyal cat...I cant imagine anyone neglecting him!