Elaine, just wanted to offer a little bit of reassurance if poss - if he's a bit nervous, I doubt he'll have gone far and if you can't find him it's likely he'll wander home on his own soon enough. Jack was once missing for a couple of hours, and despite me tramping round biting my nails, I came home, knowing that at least he's chipped, and is well known in the area. Ten minutes later he trotted down the drive happy as Larry, wet through and black as the ace of spades but didn't seem any worse for the adventure.
Wishing you all the best and hoping that he turns up safe and sound very soon if not before.