This happens occasionally with YouTube. It could be YouTube’s automated music search technology matches the track title and stops there. If there is a song title on a restricted list with the same name as a SmartSound song title, then it will sometimes be flagged.
We recommend that you e-mail YouTube directly and inform them where you got the song from. In your e-mail, include the link to the SmartSound end user license provided below. They should restore the track audio for you.