How CardRaider Works
When you delete photos on your camera, the camera doesn't actually erase them. It simply forgets where they're located on the card. As a result of this fact, CardRaider can still see the photos immediately after they're deleted. However, once a photo is deleted, that place on the memory card is now freed to be used by new photos.
If you took more pictures with your camera between the time you deleted photos and when you used CardRaider, it's likely that the older photos were overwritten by the new photos.
If you accidentally delete photos, you should stop using your camera until you can use CardRaider to get them back.