Not sure bout y'all who have been brave enough to let Apple's notoriously bad Cloud services mess with your music, but if you're doing a regular iPhone/iPad sync via iTunes, when you click on the device icon, clicking on the iPhone's Music field brings up this screen, where you can choose various music syncing options.
I know this path well, as every time I sync my iPhone, the lyrics disappear from the phone, and I have to uncheck, resync (removing all music from the phone), resync and check the box, so iTunes transfers all the tracks back again.