Sounds like a circuit is broken inside the card. Software probably won't be of much help in retrieving data if this is the case.
I've never had the issue with a flash card but, I've had the issue with other devices... where I sat on it....oops. It's like cracking a circuit board.... a microscopic circuit board. If you sent the card to the manufacturer and asked them to retrieve the data at any cost, I would bet they could do it but, the cost would be signifigant.... Just depends on how much you got paid for the shoot as to whether it would be worth it.