I've done that, and it is fixable. I took a small piece of fabric, same as the sashing or piece with the hole, matched the thread and put the small piece of fabric on the back and stitched over it a couple of times, using really small stitches. I was heartbroken when it happened, but, learned a valuable lesson... everything is fixable and you can't see the mended spot after all the quilting is done. And yes, the spot held up quite well after a couple of washings (2 by me and 1 by owner).