Help! Need help restoring artwork!

Found myself adding more music to my phone (6 Plus iOS 8.4) last night. Completed sync and noticed that there was a little more lag time then normal. Thought absolutely nothing of it until I ejected phone from computer, played a song and discovered that artwork from all 15,000+ tracks has disappeared. I've read that this can be corrected by enabling sync music, un-enabling, then finally enabling again under the music tab in iTunes when phone is connected. I've also read that this solution will also erase all my music, as you can imagine I wouldn't want to sit at my computer all day adding all my music back. There has to be some sort of way to rectify this problem.