Interesting that you asked this... I never sleep without a satin scarf so it's not a loss from friction however, the side I slept on most was always a little shorter.
A couple of months ago I moved my bed and switched the side of the bed that I sleep on and after a few months now the shorter side has become the side I now sleep on.
Actually the side I sleep on(my right side) is longer than my non-sleeping (left) side. I do sleep with a satin cap and a silky satiny hair tube on every night. This must be helping me.