Lost everything after iPhone sync--How can I get it back?
Solution 1:
If you've backed up recently, you might want to do a full restore, which will wipe your iPhone clean and reinstall iOS. After it's done that, it will offer to restore from a backup, reinstalling all apps, calendars, email accounts, etc.
http://support.apple.com/kb/ht1414
Solution 2:
I lost my photos during syncing, and the only way I got them back was using iSpirit. It's a nifty piece of Windows-only software for accessing iPad/iPhone as if was a data storage. I am quite sure it wouldn't have been deleted, just browse through and you'll find it. Good luck.