ACTUALLY HAPPENED TO ME!
Near the end of Spanish 1 in high school they gave us a test to see how much we had learned. It was a booklet with multiple pages and the teacher handed them out face down.
I tied with another student for the highest grade--70.
When the teacher was handing back the corrected tests she asked me, "Why did you leave off the 30-point question on the back?"
I had assumed that if they were handing it out face down, OF COURSE there wouldn't be QUESTIONS on the back! ...