User blog comment:BerryBandit/Mechanically demanding champions/Quick decision champions/@comment-11089105-20130622182543/@comment-4012115-20130622183200

The card last chosen can be the first card available when  Pick a Card is available again. Despite locking a specific card, the ability will still cycle the card rotation every time the card above Twisted Fate pulsates. Thus, if you throw the desired card immediately after locking it before it has a chance to pulsate again, or every three pulses after locking it, the next card will be the one you last locked.
 * Even if you will not manage to immediately grab the exact same card, counting the beats after the card you chose can still tip you off toward grabbing the same card again from the current card for the next time you activate the ability.