I've not heard of this happening before....check out this article.
http://myqbot.blogspot.com/
In short -- a woman used basting spray on her quilt and it yellowed the white backing. The yellow won't come out. I DO question whether she put the quilt in a heated dryer to fluff it after quilting.......maybe it set the spray in -- I don't know. But just an ALERT!!!! :shock: