Gold-tone chain necklace with heart pendant

I was wandering around the Plaka area yesterday around 3pm and I must have dropped my gold-tone chain necklace with a small heart pendant. It's a slim 18-inch chain, slightly tarnished, with a delicate heart pendant that has a tiny blue enamel detail. The back is engraved with the initials PM, and the clasp is a bit stiff. I think I last saw it along Dionysiou Areopagitou Street near the Acropolis Museum, in the pedestrian area outside the museum entrance. It means a lot to me—it's a gift from my grandmother—and I really need it back. If anyone finds it, please reach out; I can offer a small reward.