Why did my music vanish?

I spent a few hours the other day manually adding music from my mac to my iphone and now the music is gone and my iphone music list is back to the way it was before the transfers. Upon completion of moving the music over, my mac kept bugging me about updating my iphone from 11.1 to 11.2 so reluctantly i did. When that was finished I disconnected my phone and left. Now im looking for all that music i added but its gone. I suspect apple music or the update may have something to do with it. Any ideas?