After sleeping on a cotton pillow-case all of your life, have you ever awakened one day to find a pattern from the material engraved onto your face? This can occur when the skin begins to lose elasticity and is no longer tight and can take up to an hour before those lines begin to fade.
The solution to the problem is relatively simple. You need to take a trip to the store (where bedding is sold) and purchase a less abrasive material. I have found silk or sateen to work best for me.