Help Find Ronnie: Lost Brindle Sheppard Mix

Ronnie is a Sheppard mix black and brown brindle. He is 2 years old, probably upwards of 80-90lbs at least, he's a solid boy. He got spooked and jumped the fence around 10am Thursday morning and we haven't been able to find him at all since. We've scoured the neighborhood throughout the day and he isn't turning up. Hes very skittish, we suspect from prior abuse before we adopted him. He is microchipped but hasnt been scanned that we know of. Please help us find our boy.