Huge stationary disk

I was sailing with a friend and I had forgotten my sunglasses, so I purchased some granny glasses. The kind that fit over your regular glasses. Sailing is pretty boring when there is no wind. i was reclining looking up into the sky and I saw a circle in the clouds. My first impression is that it looked like one of those big round plastic paper clips, round with a tongue coming down the center. It was at a very high altitude and obscured by high clouds. It was so faint that I thought it might be a glare on my granny sunglasses. I moved my head up and down and side to side. The object did not move. I raised the sunglasses and the object was not visible. I put the glasses back on and it was visible. It was very faint and line pattern was white in color. so the object was a white line on a blue sky background with white clouds all around. Very hard to see. I had some binoculars just out of arms reach and I was worried about losing the object. I took a chance and reached for the binoculars. I never saw it again. The object was perfectly round and symmetrical. It did not move, with my outstretched arm, it was about half the size of my thumb. At the altitude that it was, that would make it huge. 
I will include a diagram of what it looked like, on Microsoft Visio.
Witness indicates that the date of the event is approximate.  PD