Instructions
Stop using the camera or change the memory card in the camera as soon as you realize you have accidentally erased the image. While you can no longer view the image, the file containing the picture is still stored on the memory card and will remain there until the space it occupies is used to save a new image.
Go to a computer connected to the Internet and download a recovery program such as PC Inspector Smart Recovery or PixFix for PCs or CameraSalvage for Macs. Open the program after it has been downloaded.
Insert the memory card containing the erased image into the computer's card reader or into a card reader connected to your computer. Wait a moment for your computer to acknowledge a new card has been inserted into the reader.
Click "File" in the navigation bar of the recovery software, and select "Scan/Start" from the drop-down menu. Select the icon that represents the memory card, and click "OK" for the software to begin its scan.
Click the image you accidentally erased in the window that opens up once the software has completed its scan, and save the image to your computer's hard drive. Remove the memory card from the reader to be used again.