With my dogs, rubbing their face on the carpet can mean a variety of things.
If I have just given them a bath, it is usually a canines way of drying off the ears!
First thing after a bath, dry the inside of the ear. Dogs hate water in their ears. That is why when you give your dogs a bath, you should leave the head for last. They mainly shake as soon as the ears get wet. A dog does not want an ear infection.
I take a soft flannel cloth and gently dry the ear and check it for yeast infections.
The second most common reason is if a dog has just finished a satisfying meal and is feeling good about it. He will roll on the floor, jump on the bed and snuggle in the covers. This dog is feeling good but when he rubs his face on the carpet, it is probably because he wants to get the moisture or bits of dog food off his face.
My dog will go take a big drink of water and I see the dripping beard! If I take a towel and dry the beard, he's happy again and he always lets me do it because he knows I am trying to help.