I see a black cat walking thru my house all the time. But I've never owned a black cat. The closest I have is Frantic, my tuxedo. And he's always in another area of the house.
I also fall asleep and feel my Shalimar(RB) jump up on the bed. She was smaller than my 2 boys and would always fall asleep laying her head on my foot. I can feel her purring as I lay there. When I look, no kitty.
Nothing to worry about. They're coming to you to check on you and let you know they love you!