I have a secret song from Disney instead of the one I bought

Hi. I just listened to the song, "raindeer(s) are better than people", by The Cast of Frozen in the "Frozen - Ultimate Edition" album. However, as soon as I listened to it I realised it wasn't any song from the film Frozen. First of all, it was clear that this song wasn't a finished product because it was acoustic. The sound had been completely recorded on one microphone and the piece had not been digitally altered at all. At first, I thought it was a Frozen song that sounded acoustic by error, something which has happened to me before, but it was a completely different song. I had never heard this song before but it sounded as though it was sung by the cast of Frozen, however I wasn't sure. I won't release any of the lyrics in case it wasn't meant to be released yet, but I have searched repeatedly for the song online, on Shazam, Spotify and, of course, iTunes. I found nothing. It is obvious to me that this is a professionally recorded song in its first stages, most probably created by Disney themselves. As I found no evidence of the song elsewhere, I will be contacting them later today in order to shed some light onto the situation. Im posting this here in the hope that someone will tell me if it has happened before or if it is a unique situation. An I suppose I should make a complaint to iTunes because I didn't get the song I paid for.

Cheers,

- B Humphries