I am so happy you were able to rescue your quilt!
The one bad experience I had was so bad all the white in the quilt turned baby pink... it was a very bad fabric. I refused to use pure white fabric for a long time after that but I'm very careful now in checking but even still sometimes bad things happen.
I'm a big believer in Dawn dish soap. It works so well with so many things.
BTW, I had some modern all red flannel which is usually pretty stable, but it "crocked" that is, dye transferred onto the white background print it was next to. These were pieces I bought at an after Christmas sale and just stored for awhile. Now if I don't have time to prewash and if there is anything I'm really suspicious about (for me that's reds and dark blues), I'll wrap it in a piece of the acid free tissue paper I have in my sewing room.