Just got a new iPhone SE and have been making tracks in Garage Band for about a week.  Plugged into the PC and iTunes ask something about do I want to authorize the purchases on this device or something like that.  I cancel out, change nothing on the phone, then unplug. 
After this I notice several icons are missing, including Garage Band.  After re-installing it all 30+ of my Garage Band tracks are gone.
