In experiments measuring perceptual thresholds (say of motion, color, or size), it is common that subjects say they can’t see a difference anymore between movement speeds/colors/object sizes, but, when pressed to answer the question, ‘guess’ right way above chance level.

I think it’s likely this is similar: they know, but not consciously. To test that, one could ask them whether the drawing they made represents a bicycle. I would guess many of them could say there was something funny with their own drawing, even though they can’t make a better one.

(One can have a philosophical discussion about whether that means that they know what a bicycle looks like, but they sure can act as if they know)