Dishonest advertising/marketing campaign

Wanted cosmetics and saw advert for Maybelline where purchases over R260 qualify for a gift. Unfortunately the Bluff branch didn't have the lipsticks I needed so I went to Galleria. Here I purchased the items I needed and asked the saleslady for the gift as I qualified for it. She said it was finished!!! The promotion is still valid and no mention is made of "While stocks last" so who has finished it? Was there ever such an offer or just a gimmick??? This speaks poorly of the promotions that mislead Dischems customers who are loyal to them. Can someone clarify whether such promotions are only for staff and if so why is it so widely advertised???