When you've slept so
hard that you've forgotten where you are, or you've forgotten how
long you've slept, perhaps forgetting how
long you stayed up or how you got to your sleeping place.
It's normally when you're super tired and collapse within a few minutes of lying down, or have been staying up for 24 hours.
Miles opened his eyes after pulling an
all nighter, his hardsleep ending, the
world rushing back to him after a
minute of his eyes being open.