Stuck in Oasis Quest (Fallout 3) PLEASE HELP!?

Ok so i have already played through this quest once and had no problem at all...this time I chose to destroy Harold's heart...once I left the caves I entered the the grove where dead Harold is and I'm supposed to talk to Father Treebirch to finish the quest....I talk to him but when I try to leave the grove through the door it says I need a key so I can't get through..im pretty much stuck in the grove with no way out..am i missing something??? HELP!