Lost cat, East 4th Street, 4141, Tucson - male, siamese coloring, dark brown triangle patch on chest

He is siamese colored, but larger in build than a siamese. He has slightly darker stripes on his tail and legs, and a dark brown triangle shaped patch on his chest. Eyes are almost clear, but blue, and very intelligent. He is unlikely to trust or be very friendly with unknown people, but is sweet and not unfriendly, just cautious. He has been a strictly indoor cat since I got him around 2-3 months old, and I am very concerned. He is likely to be scared of cars and any loud noises.