No free lunch

Sometimes even being a consumer have to be cautious. I recently spent on something and was given a piece of paper that said I could collect a free pearl. I read through the whole paper to get a grasp that the place to collect is next to another counter on the same floor. Nothing was mention on the paper you have to pay. So until at the counter, a pearl was extracted but it wasn't pass to me. The lady at the counter then proceed to    ask which type pendant I want on the pearl. She blabber for a while before saying the pearl is free, the workmanship is free. I only need to pay for the pendant. What crap is this? I am only to collect the pearl. So the saying about no free lunch is true. Even if they never put on the paper, there is hidden cost. They should wait for some hard core consumer who demands for the free pearl and states that the paper did not mention any cost for it. Of course I walked away.