I’ve stared at this image for hours trying to wrap my head around what’s causing this effect. The comments on the original post offer unsatisfactory explanations.
I understand the mirror is reflecting light onto the drawers, but I don’t get why the shadow is invisible. I would expect there to be a fainter shadow, but a visible one nonetheless. I’d expect the same sliver of cat shadow to manifest as a darker shadow, since that sliver isn’t being illuminated by the mirror’s light.