I expect that you told TurboTax that you DIDN'T get a 1099-B as that's the path that gets trades marked as Box C or Box F. I'd advise simply deleting the sale and re-doing it. Say "yes" to 1099-B question and select "Box B - Short Term Noncovered" on the "Tell us about your [Broker Name] 1099-B" page.
Tom Young
