User blog comment:ImperiexSeed/Supernatural Mysteries/@comment-3481504-20120501201343/@comment-3045936-20120501235712

Three theories. One cause the writers thought it would be too boring. Second, as a turing vamp as he wasn't a full vamp until he tasted blood his mind would be to chaotic or in a state of mental duress to think (Oh, Cas can you cure up this Vamp issue.) Thirdly, as a Vampire he may not be able to hear Dean's calls as while Angels can locate anyone that isn't protect by Enochian Sigils (sidenote kind of weird that they can still dreamwalk in there minds without knowing where they are even while protected by the Enochian magic.) But as a supernatural being he my not he able to hear his call like a prayer as he wasn't human or not fulling human. Again theories.