A square shaped white object that appeared as quickly as it disappeard

The sky was very clear. There were no clouds. It was a beautiful starry night. I was gazing at the stars and suddenly a perfectly square shaped object appeared as if it was resting on the earth's atmosphere. It was milky white in color. 
As I pointed to it, it suddenly zoomed across the sky leaving a faint white trail behind it. The trail could be seen for at least a minute if you knew where to look.  My companion could not see the trail.  The object appeared and disappeared so quickly, my companion did not have a chance to see it.  I just happened to be looking at the right place at the right time.  
I have never seen it again or any other unexplained objects since then and have never heard any reports anywhere of square shaped objects.
Witness elects to remain totally anonymous;  provides no contact information.  PD