After uploading iOS 5 to my iPhone, there was a message from iTunes saying that, during the procedure, iTunes was unable to backup my data. So nothing got restored and I lost a great number of photos and other stuff with no further explanation. Is there anything that can be done?
I had a similar error on my iPhone 4 iOS 5 upgrade. But mine specifically said if I proceed despite the error, all content would be lost. Did you proceed past this error?
Check your iTunes Edit > Preferences > Devices and see if you have more than 1 backup listed. Mine has 2, my current backup and my last iOS 4 backup.