iTunes says music is on iPhone, but iPhone says no content
Sorry if this has already been covered, but I couldn't find my problem after hours searching online.
I have an iPhone 5s running iOS 7.0.6, with the latest iTunes.
Today I wanted to free up some space by redownloading my high bit rate songs to my iPhone. So, I delted all the ones that were 1411 kbps off my phone, and everything was fine. That was until I tried to readd one of them, and it immediately wiped all the music off my phone. In the summary of my iPhone settings on iTunes, I now have 7.97 GB free, and no songs. On my phone, it says there is no content. However, looking at the on my device listing, under music, it still lists all 1326 songs that were previously on the phone, and the song I tried to add is listed in grey, as being waited to download.
How can I fix the missing music, and prevent this in the future?
Thanks
iMac, OS X Yosemite (10.10.1)