I had this happen to me about 3 months ago. I purchased a necklace from a seller, and when I received it, it arrived broken (it was all turquoise). I was so angry but I was very nice when I left them an e-mail explaining the problem. He was very nice and friendly and advised that I ship back immediately, and as soon as he receives it, he will immediately send me out a replacement—I also said that I should have my return shipping fees refunded because it is not my fault that the necklace arrived broken and I had to ship back to him. He agreed.
However, once I received the replacement, it was in excellent condition, but completely forgot about the "promise" he made about refunding my S&H fees (back to him), so I left positive feedback right away. Well, the schmuck never left me feedback and never refunded my shipping fees.
I even contacted him a month later and asked why he hasn't left me feedback, especially in light of the situation? Not only did he never respond, but he never left me FB (maybe to be spiteful???). So now, I will NEVER, EVER purchase anything from him again, even though his CS was good, he went back on his word and never left me FB. I think that's crap, IMO.
EDIT: I forgot to add that I also checked his FB activity that he left for others, and he was VERY consistent on leaving FB for other buyers, just not me.