Medium black/white dog with blue collar, lost near Main St

I’m really worried—yesterday around 3pm my dog slipped out of his leash near the Starbucks on Main Street in downtown Las Cruces. He’s a medium-sized black and white border collie mix with tan points, about 45 pounds, short coat, and a bright blue collar. He has a small white heart-shaped patch on his chest and a little notch in his left ear. There’s also a faded bone-shaped tag on the collar with the name 'Rex' and a microchip tag. He’s friendly but gets nervous around strangers; I just want him back home, he’s been with me for 6 years.