Large rectangle translucent grey white with giant circles

I was leaving work. I notice the sky in the back parking lot where it's generally very busy . It felt like time stopped but I didn't and the craft didn't. I saw a large translucent rectangle with large circles. It was matte and floated and disappeared into the sky. I looked around to see if anyone saw it as well. There were no cars no people and that's quite strange for this area. I feel like it could be a larger craft but I only saw a small section