We also have a 'Pet Search' in our local paper where you can advertise lost and found pets, its free for the first week.

Leave a pet carrier in the garden near their usual sleeping/play area, put a familiar piece of bedding/blanket in, big bowl of yummy food and a water bottle then if he comes back he should find it, have something to eat and drink and then curl up for a snooze and should still be there by the time you spot him.

Also if you play with squeeky toys etc with him go and walk around the area squeeking it