How does the author use foreshadowing in The Necklace?

After losing the necklace, Mathilde visits the jeweler whose name is on the box of the necklace Madame Forestier lent her. His response, "I didn't sell that necklace madame. I only supplied the box," foreshadows the necklace is not what it seems..... not the valuable piece Mathilde believed it to be.