it could happen, and is actually more common than you would think, ive seen artists make that very mistake before. ive also seen artists paint two left hands on a painting before...lol...and then there is also the times when artists will do things on purpose just to see if anyone ever catches it, theres a tradition of painting hidden pictures within the main painting also, whether done with shadows or just hidden somewhere in the painting..... i used to put something in the eye reflections on almost all digital work, just cause i could...lol.... when michelangelo carved the statue of "david" he made the right hand over sized to draw the gaze there. he also made the head and neck too large (along with undersized genitalia) so as to pull the viewers attention upward....and then made the eyes looking in different directions to hold the attention for a little longer. (the mind will stay focused wondering just what is off.......a perfection through imperfection trick....wabi-sabi if you will). and yet this work is thought to be the most perfect, beautiful sculpture ever made, of which i do agree