Gold necklace with heart pendant, sentimental keepsake

I dropped my gold necklace yesterday around 3pm near the Brownsville Historical Museum on Ringgold Street, by the cafe entrance outside. It's a delicate 18-inch, unbranded 14k gold chain with a small heart pendant that has a tiny sapphire at the center. On the back of the pendant there's an engraving with the initials 'LM' - a key identifying feature. The chain is in generally good condition, but the clasp is a bit stiff and there's a faint scratch on the pendant. This necklace was a gift from my grandmother and it means a lot to me; I really need it back.