What do you think about this photo?

That is a beautiful photo. I am not sure why it would be rejected in a photo contest, but perhaps because it didn't have what the judges were looking for.

Cool unique type of portrait. I do not know what kind of contest you entered it in, but there could be many reasons for rejection. Probably most likely that the judge of your photo prefers a portrait to include the whole face, as personally if I was asking for a true portrait photo I would want the whole face in the portrait unobstructed.

I like it a lot. I have always been a fan of black and white photography. I can't understand why this one would be rejected.

It depends on what the photo site or contest was looking for, clarity, originality, sharpness, hue, contrast etc... whatever it lacked was not told to you right? Why it was rejected ? I don't think 'hiding behind mask' is an appropriate title but maybe 'tweaking innocence' is better . . .