A childhood belief about imaginary friends

When I was younger, my imaginary friend was Sirius Black from the Harry Potter series. I pretended that he went everywhere with me, and often told my parents what he had said to me that day at the dinner table. Then one day I was sitting on the stairs talking to him, and he suddenly just walked through the wall and disappeared. I yelled "sirius come back" and tried to follow him but of course I ran into the wall. I never could manage to replace him.