Gray Syrian hamster missing from blue cage

I lost my gray Syrian hamster, Niko, yesterday around 5pm. He’s about the size of a ping-pong ball with soft gray fur and a white belly, and he wears a tiny blue harness when I take him out for a stroll around the apartment. I last saw him near the Walmart on West High Avenue in New Philadelphia, the parking lot corner by the garden center. He has a small white patch on his chest and a slightly nicked left ear, and he’s fast as lightning when he’s scared. This little guy was a rescue and means the world to me; I would really appreciate getting him back safe and sound.