A deep sleep had fallen upon them, and so what happened at their very heads they neither saw nor knew. This is not only the sleep of the body. Most of a human life is lived in exactly this state, lost in thought, absent from the present, moving through events without ever truly being there for them.
To be unconscious is to be asleep with open eyes. Life comes close enough to touch you and you miss it, because you are somewhere else, inside the endless commentary of the mind. Waking simply means becoming present enough to notice what is actually here, which is the one thing the sleeping never do.