Perhaps the Spirit, knowing his heart better than you or I, led him to pray for Mary’s help.Obviously it was the right thing for him as she gently suggested confession which healed him.God knows what we need and uses many avenues to help, so boundless is His Love.
Again, we have no Scriptural support for the Holy Spirit directing us to pray to anyone other than Jesus or God.
Confession is not what heals....belief in Christ is what heals.