How to recover a deleted save file in Pokemon Gold Virtual Console

Commonly with virtual console games, you can hit the center button (Wii menu?), and exit the game. This will automatically save the state of the game. Next time the game loads you'll begin at that spot; however, after reloading once the save state is no longer available -- resetting the system won't allow you to resume from that state again.

Unfortunately, when your nephew created a new save file a significant portion of the data will have been overwritten, so complete recovery is impossible and even partial recovery is completely unfeasible. The cartridge only has a limited amount of memory to write on. In order to make room for your nephews save, it had to make new space by writing over place where your data was. Since the kind of sophisticated programs used for hard drive recovery are not available for gba cartridges, you are out of luck.

The difference between recovering data from a computer and a cartridge is a combination of the lack of programs and access to the cartridge, and the fact that the creation of a new file overwrites a significant amount of data. Its not like a computer where the data is still there but not easy for the computer to find