Lost dog: grey/white terrier with red collar

I lost my grey-and-white terrier yesterday around 3pm near Barnes Crossing Mall in Tupelo. He's about 40 pounds, short-coated, with one floppy ear and a white heart-shaped patch on his chest, and he wears a red nylon collar with a small round tag that has my phone number. He can be shy around people but is incredibly friendly once he warms up. He bolted when a loud car backfired near the Belk entrance and wandered toward the West Main Street neighborhood; I haven’t seen him since. This dog means the world to me—he was a rescue and helps me through tough days—email me at [email protected] if you've seen him.