I used to work for Joann's and yes it's true that some of the management can give off the attitude of "not my problem" but the two different store where I worked had great managers. Both were more than willing to "make things right" for customers. Since it's been so long since the fabric was purchased, I don't know what can be done. I do feel bad for you especially after all the work you've put into your quilt. My suggestion would be to call the Joann's store where you purchased it, ask to speak with the manager, tell him/her what happened and ask what can be done about it. Sometimes it helps to stay calm but at the same time let them know you WANT some kind of resolution about the problem. If that doesn't work, go to Joann headquarters -- ask to speak to the complaint's department. I wish I could remember where that is but I don't. One last thing --- Please don't take out your frustration on the sales clerk. They had nothing to do with what happened to the fabric.
I"ll bet that something happened during the weaving process of the fabric that made this happen. Who knows.