No longer available to players. You can safely vendor this item or hang on to it for nostalgia's sake. Or try to sell it - there are collectors for nearly anything in the game.
Morrowgrain, prior to Patch 4.0.3a, was both a quest item and a crafting material. Since the quest that allowed players to (rather haphazardly) acquire morrowgrain was being removed for Cataclysm, Cenarion Herb Bag had its mats changed.