What do you mean by "suddenly formatted"? Do you mean that you've accidentally formatted the the SD card?
I'd recommend that you try the SD card with a different computer and/or device, to see if it's recognized, so that you could try and reformat it again and see if that fixes things up. You could also try to download its manufacturer's formatting tool, to see if it recognizes the card and if you can use it to reformat the memory card.
Hope that helps. Please let me know how it goes.