Hi,
A man of few words
Yes, it is interesting that maybe we are just seeing the shadow of reality in everyday life.
The actual physical reality of the peg has only incidental relationship to the shadow. It can be on top, all the way through, only partway through, or even riding on a thin surface of light oil ... we'd never know from a limited viewpoint, but in all cases we see the shadow unless of course there was a drastic change such as the entire removal of the peg.
If for some reason we could not see the peg, we'd have to try to infer its presence from the shadow. That's all we would have to go on.