I lost my saved data. What should I do to recover it?
Though there is really no guarantee that all saved data that are believed to be lost will be recovered, you have to check your savetype all the time so lost of data files will not happen to you. This is the basic step that you can do to avoid this accident from happening. Still, there are instances where data can still be saved even if the savetype is incorrect. Unfortunately, this does not guarantee that once you make use of your saved file once again, it will be working properly.
No$GBA Save Games : No$GBA Save My Game
If you already think that your files are lost, try remembering if you have changed the game name or folder of your saved types. The emulator will only recognize data that are named properly and accordingly. So if you have done certain changes, do the same with all the files related to the first one. This will keep you from losing more of your data.
Additionally, you can always check out the backup file that you can find in the hard drive. But this option is only possible if you keep a backup file before hand. If you have not done this before, then you better start doing this.
Another suggestion to avoid losing more of your files in the future is to reload your game frequently or saving it occasionally along the game to make sure that you can keep a file on it. Remember that once the emulator crashes, your previous games that are not properly saved will not be recovered anymore.