Dwarf hamster with heart-shaped chest patch

I lost my dwarf hamster Mochi yesterday around 3pm near the Patee House Museum on 3rd Street in downtown St Joseph. Mochi is tiny, walnut-sized, with a sandy-tan coat and a white belly; there's a little heart-shaped white patch on his chest and a tiny black tip on his left ear. He was last roaming in his lime-green harness with a tiny bell, and I’m worried someone might have picked him up. He means the world to me, especially my kid, and I’d really appreciate any sighting or a quick return.