Silver Dust (Tapit), who scored in Saturday's GIII Mineshaft S. at Fair Grounds, has been disqualified and placed last for his previous victory, in the GIII Louisiana S. Jan. 18, due to a failed drug test, according to a report in the Daily Racing Form. The Bret Calhoun-trained gray tested positive for levamisole, the same drug that got eight Joe Sharp trainees disqualified from wins at the meet earlier this month. Calhoun is married to Sharp's mother, Sara Escudero, and the two trainers' barns at Fair Grounds are next to...