From Celtic Myth Podshow:

It is said that Aengus was troubled by dreams and visions of a beautiful, young maiden. He fell in love with her immediately and started to waste away because he could not find her. His mother Boann searched the whole of Ireland for the maiden, but after a year she still had not found her. The mighty Dagda did the same and also could not find her. Then the great and wise Dagda called on Bodb Dearg, king of the Sidhe in Munster and the Dagda’s aide, to go and find the girl, and she was found at Loch Bel Dracon (the Loch of the Dragon’s Mouth), chained to fifty other girls, all of whom turn into birds.

I wouldn’t recommend asking a King of the Sídhe for help unless you’ve got some serious god cred of your own, however.