Thank you for this original post, Gem. My first reaction was to think about it. Assume I could be "smart" and say it was our cosmic essence, and go on to describe it in the hopes of being praised for accuracy.
And then I realized, perhaps the question wasn't meant to be answered. A practice for consciousness instead, presented as a means to spark a connection into the sensation that you mentioned in a following post; about being left in a place - a void, if you would, that is both nothing and everything - full of possibility of form or non-form. Perhaps this was what you meant, or maybe not. But regardless, thank you for presenting the scenario.
"Sometimes you will act as an angel to someone else, perhaps without even knowing it. One day someone comes up to you and says, "You saved my life." You look at her astonished, trying to remember when you even saw the person before, the meeting meant so little to you at the time. "Don't you remember? I was standing on the bridge, staring at the water, and you passed and said, 'Good morning'."