Well, I got it back and looked at it. Interestingly enough, it's pretty much the same fabric that's shredded and come loose, but it's one color out of a bunch of fat quarters I used of the same type. I had about five purple fat quarters in different shades, and it's only the one shade. So why only one would fall apart, I don't know. I am not going to fix it because it's quite likely it will just fall apart in other spots since that fabric is faulty.
Also, the batting (a polyester) has completely shredded inside. I only tied this quilt, and yes, I didn't tie it every five inches or whatever the instructions said, I confess I slack on that, but still...the batting is a complete mess inside. I only made this last year. I've been using Warm and Natural cotton batting since, and I think I will stick with that in the future.
It's all very discouraging...