So i just spent the past 2 hours syncing music over to my iPhone and it all got "erased"

So I just got done syncing almost all of my music form iTunes (12.3.3) to my iPhone 6s (iOS 9.3.1) except for 2 songs. When i tried to sync them over i got an error message saying that saying that some of the items are not able to copy over to the iPhone because they were not able to play on the iPhone. Then underneath it was a list of 100 other songs that were unable to play on the iPhone 6s. I have had many other problems with iTunes before and this type of error message has sprung up before so I knowingly checked my iPhone immediately to check if all my music was gone. About 90% of the music I have just spent the past 2 hours syncing over were in fact gone! Only a couple songs were still on my iPhone (besides the few ones I had boughten through iTunes in the iPhone app) leaving me with 100 less songs!

Next I went straight to iTunes to try and resync the music over and iTunes acted as if the songs were already on my iPhone (if you don't know what I mean, try to sync an album over to your Apple device that is already on said Apple device). Which means that the music was somehow on my iPhone but not showing up in the music app. This is the problem I'm having, iTunes thinks that I have the music already on my iPhone when I don't.

All the music is .mp3 format, and it has been on my iPhone before so I don't think the files can be corrupt or not compatible. Only thing I can think of is that this is some iTunes glitch since this has happened to me before.

Any other info I need to provide just ask for and I hope we can get this problem solved asap.