When looking for Hexproof creatures in the current standard, Sacred Wolf is not listed with them. When going to the Sacred Wolf page - http://deckbox.org/mtg/Sacred%20Wolf - , it only has the M11 text which does not explicitly say Hexproof so being excluded is understandable, but the M12 text does say Hexproof and I would think it should be searchable.

What other cards are potentially left out of searches due to rules text changes?

We've updated the rules text of Sacred Wolf, thanks for reporting.