IPhone/iTunes Album Artwork problem

Had my iPhone for months and a music library on iTunes and the phone in the 1000s and nothings been wrong but yesterday I plugged in my iPhone to charge on my PC and it wouldn't sync it popped up saying ''iTunes can't read contents of the iPhone, please restore'' or whatever so I chose not to because I would lose my stuff so I just downloaded iFunbox and deleted the music file which was recommended by people to do with the same problem and that worked fine and it deleted the music from my iPhone but at least it was out of recovery mode and could be synced now

Spent HOURS syncing the right music back on to my phone and once everything was done I plugged it out and not a single song had an album cover, I've bought my fair share of iTunes music but most of my library are downloaded MP3's. Whether I bought it from iTunes, used 'Get album artwork' or manually put in a cover on 'Get info' every single song I had had a cover and now on my phone none do. Not my ones or the Store ones.

But the thing that's annoying me is that on my actually iTunes music library everything's in tact with all album covers, I've tried EVERYTHING I've cleared my phone and tried syncing several times to my library and its just not working.

iPhone 4S 6.0.1
iTunes 11.0.1

Could you convert the format of the music files via iTunes to AAC or whatever is the original way it was when you downloaded it? Not positive it would work for you but it is all I could think of… Also you could try asking this question on the iTunes help page or make an appointment with the apple Genius Bar ( an apple store ) in your local area to see if they could help you fix the problem

All the songs need to be in AAC format