It appears there are many discussions about this.

by R. Proffitt Moderator - 11/30/12 10:27 AM

In Reply to: What happened to my iPhone 5, iTunes playlists? by wbb56

Be sure to read what they turned off and on at
https://discussions.apple.com/thread/3872611?start=15&tstart=0

And call it in. Sounds buggy.
Bob