I do this all the time: I'll have a flash of an idea and I'll jot it down, fuss with it for a while, and then realize that it's not going to work out. I'll save the drawing, file it, and forget it.
While I know that this was for the Noo Tarot, I have no idea what card I was working on, but it was probably for the suit of Ankhs. And it was only a month ago. I have dozens of "sketchbook" ideas -- from antiquity until now -- that leave me without inkling as to their original purpose. You'd think I'd be making notes on them by now!
What this shows, though, is an example of the bold colors I use when sketching so that I can see the shapes with which I'm working. The garments would have eventually become white, the wings probably golden, and Lord knows what on earth I was thinking with the headdress. One thing is certain: one of these days I'll need this drawing for something and there it will be, ready-made.