Text (AN/RV+errata): {2},{Tap}, Discard the last card you drew this turn: Draw a card. [Oracle 2005/08/01]
If you do not have the card still in your hand, you cannot pay the cost. [DeLaney 1998/07/02] There is currently no way to prove that it was the card you drew except to get a judge or 3rd party involved, or to put cards you draw aside until you decide whether or not to use this.
If you draw more than one card due to a spell or ability, you must discard the last one of those drawn. [DeLaney 2000/03/17]
Extended tournaments (see Rule 913) have banned this card since 1999/10/01.