This is a trick matter, since it depends on where are your SMS being saved. If you have saved the information on your mobile phone SD card, its possible to recover them since the files on every SD Card don't get erased immediately.
When a file gets deleted from an SD Card, the space occupied by that file get marked as vacant so allow subsequent files are written on that spot. So, unless the space already been overwritten by new data, your deleted SMS thread is still there and can be retrieved.
Lets go step by step:
You will need an SD card Reader and an SD card Data Recovery software.
Memory card Reader
A memory card reader is a device, typically having a USB interface, for accessing the data on a memory card such as a CompactFlash (CF), Secure Digital (SD) or MultiMediaCard (MMC). Most card readers also offer write capability, and together with the card, this can function as a pen drive.
SD card Data Recovery
Card Data Recovery is professional digital photo recovery software to recover deleted files.
The software has two versions: Card Data Recovery for Windows and Card Data Recovery for Mac.
It was intended to recover photos and other file types, but actually, you can use it to recovery any deleted file.
Download the trial version and install it.
- Remove the SD Card from your phone.
- Put the SD Card in Card Reader and connect it to the USB port of your computer.
Run Card Data Recovery:
The SD Card will appear on the drives list, under "Removable media".
- Select by clicking it. Once selected and orange arrow will appear.
- At the right side, you see a big button labelled "ALL", press it (a green tick will be present on the upper right corner of the button).
- At the bottom, press the gray Scan button to start the scanning process on your SD Card.
A message saying "Scanning, please wait..." will appear, wait until it finish.
When the scanning is completed, the program presents you with the recovered files:
- select what you need to recover.
- Press Recover to start the recovering process.
If your SMS's are there, buy the application ($24.95) in order to finish the recovery process.
Other recovery applications
Perform a regular backup of your phone contents to your computer. It comes handy when having to restore deleted stuff from your phone.