I wish I could say I have no idea how that feels, but, I totally sympathize.
I finished pressing a quilt top that I pieced today. Made with Moda charm pack and Kona cotton. Found a 2 inch weaving flaw in a piece of the Kona. It's all stitched up in the middle of the quilt. I was fit to be tied!
When you pay good money for what you believe to be good fabric, it can really make you angry to find a flaw AFTER you stitched it in.
I just hope that quilting will make it disappear.