Many cats that are not used to being outside go to a place quite close to home and "freeze," too frightened to leave their new sanctuary. Walk around the neighborhood calling his name and shaking biscuits. Stop and listen every few steps, as he may be too frightened to emerge but will cry or call out. He's also more likely to venture out after dark, so call him then. Put posters up locally with a photo and a contact number, and ring the local vet clinics or shelters to see if he's been handed in.