You did RIGHT! Taking that dog into your home would have been like me taking a cat that hated being around other cats. The dog you foster be suitable to live with and fit into your family. as you do not know how long it will be with you.
It might take some time to find you your first foster. I started to wonder if they even WANTED me when I offered to foster. But believe me, they DO want and need you. Hang in there for a better fit.