Solution on How to Restore Deleted Facebook Messaes
Step1. Download & Install iPhone Data Recovery (Mac)
Download and install iPhone Data Recovery (Mac) on your computer and launch it.
Connect your iOS device with your Mac
Run iPhone Data Recovery and connect your iPhone to your Mac computer. Then you will see a window as follows:
Choose the recovery mode of "Recovery from iOS Device". Move to next step.
Scan deleted Facebook messages on iPhone
Click "Start"button in the window to scan deleted Facebook messages on iPhone. If you use iPhone 4, iPhone 3GS, click "Advance Mode" to have a deeper scan for deleted Facebook messages. The scanning process may take you a few minutes.
Preview & Retrieve deleted Facebook messages
From the left column of this window, you can see Facebook messages. Swipe the top button to the left to only display those deleted items. Choose ones you want and click "Recover" to get back your data.