As I recall the story, Allen thanked Nixon for the play and told him he'd run it, then when Nixon was out of sight promptly crumpled it up and threw it in the trash.
I remember it as some goofy fake field-goal that was supposed to be a pass to the wide receiver who replaced Charley Taylor, who had broken a leg against the KC Chiefs. Clifton McNiel? True, though...any trick play would have been against Allen's nature...letting Sonny pass was against Allen's nature...in fact, doing anything on offense more creative than handing the ball to Larry Brown was against Allen's nature.