I believe that the Wampa hand-puppet prop used in the attack-short had horns, just that they were covered over with white fur a little bit too much when the prop was made. What could be perceived as darker patches in his high cheek bones (...) are the horns.

I think those features should be used as starting points when painting the new horns, and let remain somewhat obscured, but not as much as before.

Btw, the hand-puppet has quite prominent ears, just that they are not seen from the angle used in the first shot.