I saw the shadow of a stealth object

I was 15 years old never touched any alcohol or drug at that time. I was sitting outside on the steps in my backyard facing the street. It was a beautiful summer day and I had noticed when I came out to sit on the steps that there were no clouds in the sky at all. As I was sitting there I noticed a shadow moving in front of me and I looked up above me to see what was making the shadow and saw nothing. The shadow was rectangular in shape the size of two cars side by side and it followed the curve of the road. I looked up again to make sure that there wasn't a cloud or a plane or a helicopter but there was nothing and no sound of anything. It was silent and I watched it follow the road down as far as I could see it go.
It was after the shadow had gone that my neighbor came out and asked me what was wrong and I told him.