I found two theories on Hitchcock's belly button -

One
He had his bellybutton surgically removed, because, according to him, he thought they were disgusting.

and 2nd -

he 'lost' it when being sewn up after surgery.

( from knowing that he was, in the 1930's - about 300+ lbs, and later lost a great deal, almost half, of that weight - my guess is that he had alot of skin that was either specifically removed because of the weight loss or as part of some other surgery.)

laura