My sister swears she saw this happen when she was in college:

One night in the library my sister and some of her friends were sitting around a table studying. This one woman was having a hard time staying awake. Just as she nodded and her eyes closed, the power went off and the library went dark. She opened her eyes again and screamed "I can't see!" People snickered, she sobbed, "This isn't funny, I can't see anything. Something terrible has happened." Just then the lights came back on and one very mortified woman ran all the way back to her dorm.