Here are some ideas of how I would do this.
1 - Do not write anything onto the card.
2 - Make several backups of the card thus so that it isn't lost and several restore methods can be tried:
-- a - Copy the card onto PC using windows and using KN-SDExplorer (do not let KNSDE try to fix the card at this point).
-- b - Copy the card onto another card using disk copying software such as macrium reflect.
-- c - Make a low-level copy of the card using runtime software's getdataback.
3 - Open the COPY card with KN-SDExplorer. Don't allow it to make a fix. If you can see files in KNSDE you'll be able to copy them to another card using KNSDE.
4 - Try a fix with KNSDE. It will attempt a fix. Usually, only one style will be corrupted, but they might all lose their names.
5 - Try getdataback. I've had the most success with this. It can often find the entire previous version of a card, even if you have formatted it. It is paid-for software. I have it if anyone wants to post a card to me to try.
6 - Worst case - In windows you should be able to see all the files within the PRIVATE folder on the card. They will have nonsense names but they can be copied onto another card (drag and drop on KNSDE), and then renamed.
Finally, everything I said about KNSDE above also applies to Techmanager2000, which is a very comprehensive and professional tool.