Iphone deleted all my music?

I recently updated my iPhone 5s to iOS 8.4. Last night, i synced my iPhone to my iMac iTunes library and copied all of the music on there to my iPhone. Everything was fine until this morning when I looked and discovered that all the music from my phone had been deleted, including the purchased tracks. I rebooted, nothing came back. I took a look at the storage manager in my phone and about 7 GB of memory was missing ( it said i had used 11 GB, but when i added all of the amounts of storage it listed below, it only added to about 4.5 GB). I know that my music used to occupy the most amount of storage on my phone, so I think it is still there. I can't plug it into my computer for a few days. Has this happened to anyone else? Please answer this!

Ya. Even though both are apples products, they suck when it comes to syncing. I've done this once before too. It Doesn't sync from your phone to your computer, instead, it syncs from your computer to your phone. Meaning it deletes everything on phone and replaces it with everything on your computer… Which is nothing. Luckily, iCloud saves all of your music, so just redownload everything, and you will be set. I deleted iTunes on my mac for this very reason… It actually happened to me a few times…

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