Mosiah 27:14

"And again, that angel said: Behold, the Lord hath heard the prayers of his people, and also the prayers of his servant, Alma, who is thy father; for he has prayed with much faith concerning thee that thou mightest be brought to the knowledge of the truth; therefore, for this purpose have I come to convince thee of the power and authority of God, that the prayers of his servants might be answered according to their faith."

Because of prayer and faith an angel came down to convince Alma the younger of his wickedness.  Prayers of faith are always answered.  Angels may not be the messengers of those answers, but they are still answered in whatever means the Lord sees fit.  This miracle happened because a people united in prayer over the welfare of wayward sons.  It is amazing how great things can be brought to pass through prayers of faith!