No the ally has to be discarded from play. A similar question has been asked about the card Crypt Chill (Core Set Treachery) which also discards assets from play.
While your control argument is correct, the ruling is based on the "Ability" entry which says:
Rules Reference, pg 2 wrote:
Card abilities only interact with other cards that are in play, unless the ability specifically references an interaction with cards in an out-of-play area
And cards in your hand are considered out of play, even though technically under your control.
Edit: 'd by Yury