To recover deleted massages on an iPhone 4, you need to connect your iPhone to your computer using the USB cord. Wait for your iTunes program to open and select the "Sync" button. Wait for your iPhone information to complete updating and remove it from your computer. Open the text message application on your iPhone and the message will be presented when it was last synced.
2. Else you can simply get a iPhone data recovery software which will extract and recover the data for you from the iPhone's backup. I'd recommend that you use Total Saver to keep things quick and simple. You can read about the software following the link below:- http://goo.gl/BYuljf