I know first hand someone who have driven several kilometres only to "wake up" and not being able to explain. This is of course extremely dangerous and in every case I know of it has ended with a damaged / wrecked car though luckily no injuries or fatalities. (Back country roads, middle of the night etc).
What happened in at least one of these cases was dreaming with eyes open. From what I hear that might not be to uncommon but here I'm back to old wives tales.
There is a case to be made with these situations that you weren't actually asleep.. you just didn't lay down memories for the period of time, because nothing happened.
You feel like time is missing because you have no recollection of that time - but that does not have to equate to you not being awake, or able to respond.
What happened in at least one of these cases was dreaming with eyes open. From what I hear that might not be to uncommon but here I'm back to old wives tales.