I am so sorry that this happened to you. I had a similar situation once, but with some black fabric used on the front of the very first quilt I ever sold. Fortunately, he was understanding, and since it was a Roman stripe quilt, I cut triangles slightly larger than the triangular piece, appliqued it down by hand, then quilted new lines to match those on the quilt. I just think you got a bad piece of fabric, like I did, either something chemical or sunlight damage I'll never know, but fortunately I was able to repair it. My only suggestion would be to replace the backing fabric, use enough quilting to stabilize it and may be replace the binding by cutting it off and adding a new binding.