Place his litterbox and some smelly wet food such as tuna fish outside. If
You have a garage leave door cracked and place food and water inside.
Check with your neighbors and ask them to check their garages and sheds.
Late at night walk and call him shake a bag of treats or dry food.
Fliers are crucial post them door to door and on poles.
Make a missing report with your shelter and then check back every couple of days always in person.