Lost: Black-and-white border collie mix with scar

I lost my dog yesterday around 6pm in Joplin. He's a black-and-white border collie mix, about 50 pounds, with a small scar above his left eye and a white blaze down his chest. He wears a neon green collar with a metal tag showing my phone number, and he tends to wag his tail nervously when he sees strangers. Last seen in the Walmart parking lot on Range Line Road near the 20th Street entrance; he will sometimes bolt toward cars if he gets scared. This dog is family to me and my son—he's helped him cope with anxiety, and he has sentimental value. If anyone spots him, please text me; I just want him home safe.