There was always the chance that someone may have beaten him to it,without his knowledge. At the same time,after the deceased had been moved,he could have even stayed at WHF on the pretext that it might be burgled.That way he could have gone over everything with a fine tooth-comb.
After all,it's alleged that he committed the murders and for that you've got to have a mind of steel,so staying while empty of occupants isn't going to bother anyone,least of all a killer.