I routinely rate songs on my iPhone in the Music app with the 1-5 star system.
I just plugged my iPhone into my computer and saw in iTunes (on the "Music" tab under "Devices") ALL OF MY SONG RATINGS ARE GONE. When I right click on a particular song and click "Get Info", the star ratings are gone from there, too.
How can I see the star ratings in iTunes?
OS X 10.10.4 (2013 rMBP) -- iTunes 18.104.22.168 -- iOS 8.3 (iPhone 4S)