Someone responded on an earlier post on this subject to the freezing issue. She is a long arm quilter. If she ships a quilt back to a customer, it may be subjected to freezing temps en route.
Don't know of any other way it might freeze. And my understanding is that you would need to iron again to get it to disappear. Wonder if washing removes it permanently? Or maybe just a hit of steam from your iron?
I wouldn't use one of these on a check, though!