I have returned fabric to Joann's before. I bought about 5 yards in the store, in a hurry, and when I got home and looked at it, I could see my hand through the fabric. I did return it.
I wish I had returned some of the ugly fabric I bought there once but it was gifted to someone making pet beds and she was thrilled with the donation and the shelter animals didn't care either.
I have bought fabric with a flaw before because it was exactly what I needed and there was enough to work around the flaw to get what I needed for the quilt.