Mosaic, it's not just a cat, and we all share your anxiety. It is the spring and cats go a-wander. One of mine got shut in a garage on Christmas eve when he was a kitten, fortunately someone went to get the car out at midnight. Cat 1 went missing for 3 days when the men were fitting my boiler... Is your puss microchipped? I hope so, then if he's handed in or anyone finds him, the vet can ID him and ring you. Put up notices, ring the Cats protection league or your local cat home, ask at all the local vets. They're used to it, they won't mind. I wish you and puss well.