Delicate 18-inch gold necklace with sapphire pendant

Yesterday around 3pm I realized I'd lost my delicate 18-inch 14k gold necklace near the La Salle County Library on Elm Street in La Salle Co. It's a heart-shaped pendant with a tiny sapphire set in the center, on an 18-inch fine gold chain. The back is engraved with the initial 'A' and the clasp shows a small, barely-visible scratch from wear. It was a gift from my grandmother and means a lot to me; I'd be really grateful to have it back.