I tried the same thing last month, but the card was formatted in the C300. I used 5 different recovery programs, both PC and Mac, with no such luck. I was able to recover some files, but post couldn't get any of them to work. I came to the conclusion that the C300 does some permanent erasing when formatting, unlike the 5D. However, if it was just "erased", it should all be completely recoverable. +1 for Recuva.