I don't believe a mummy resides in the Great Pyramid. Just my opinion, but there is not one funerary drawing, incantation, or tribute painted or carved for the dead Pharoah. It's chambers and corridors should be filled with the temple arts to insure the Pharoahs successful maneuvering through the land of the dead and weighing of the heart.
There should be temple arts still there and yet the walls are bare.