Place the towel in the cage kinda balled up. Put it in so that it can be crawled through and rubbed against not just slithered over and under.

Being that Im not there I can only judge the situation by what you have described. Its sounds to me that it is stuck. If it started by accident or not the skin should still come off with little fuss. The fact that it has not makes it seem to be stuck. I don't think it is a big issue and I truly believe misting and a towel will clear it up for you.