You should be able to recover the image. Just don't use the card again in the meantime, or you'll start overwriting it. I use Rescue Pro, which came with a Sandisk card reader, but there are plenty of other utilities to do this and I'm sure someone will post details. A decent camera shop will probably have the software too, but they'll probably charge a fee. Might be worth paying if you're not very confident about doing it yourself, but it's quite simple and I'd get the software just in case you have another hiccup. It happens!