I don't know for sure, it might vary district to district, but I haven't seen any in probably 3-4 yrs. They would walk the store and record who did/didn't ask CIHYFS ask to sign up for a Target Visa. They may have looked for more, but that's what I remember. Sometimes the people who did things correctly (ask CIHYFS and/or about red cards) would get a $10 giftcard. It was kind of cool, but now I think the under cover visits are more ETLs/STLs going from store-to-store undercover and recording what they find.
Oh, and to answer your other question, yes, the stores were told the results as soon as a visit was over.