I'm very sorry for the loss and as people have stated already dont format the drive and try to recover the data with any of the type of tools mentioned here. And data recovery does come in many variants of prices aswell depending on how much work is needed. If its just a messed upp FAT table for example it may be solved in minutes.
But regardless i would like to mention my own backupsystem that i use and the philosophy behind it. Yes, it's based on harddrive backup as this is the cheapest form of high-volume backup today. No, i do not trust harddrives one bit. I've had too many fail on me to do that

So whats the trick then? Redundancy. And a lot of it.
I run one main hard-drive which is my work-drive and separated from the OS drive btw. This drive is then mirrored to two separate drives, both external. This is done every evening and it only mirrors the changes. In additional to this, every week i make a 3.rd mirror to another external drive (or more often if ive had a major job that week) which is brought OFF site. This is the last resort backup in case i get burglared or the studio burns down.
Now thats the technical setup, with quadrupel redundancy in worst case, and quintuple in best case. If you are doing the math and wondering where i got the magic 5.th backup from or the 4.th if i cant use the weekly backup, this is the memory card. I said i back up at the end of the day right? This also means i am NOT clearing the memory cards until the backup has been done. Memory cards are cheap and a good way to have extra backup.
In addition to this, i also quite often shoot tethered to a laptop which brings in another level of backup as i always shoot and save both to card and computer. This has actually saved me once when the card failed before it could be transfered to my editing computer, and the pictures from the shoot were still on the laptop.
Now, i started off by saying i dont trust harddrives right? Well here is where the lack of that trust comes in. A normal harddrive has a lifespan of 3 to 5 years. Manifacturers sometimes state higher years but that is usually not with full usage and writing to it all the time so i err on the cautious side. So here are a few rules iv'e set for this backup solution:
1) If one harddrive fails, i change ALL harddrives. This may sound extravagant but in reality the cost isn't much at all considering it's extremely unusual for it to fail before 3 years. And especially if you got harddrives from the same batch it may be an error in that batch so if one fails, the others will follow soon most likely.
2) after 3 years, i change all harddrives again. Or if i need to upgrade to larger volumes, i also change them all. All this changing is due to the old rule that the backup/security system is never stronger than the weakest part of it.
3) never remove anything until it's been copied to the daily backup system.
This is what i would describe as a dynamic backupsystem where you keep the copies alive and changing all the time, as opposed to a static backupsystem which means you make one backup and then put it away thinking it is safe. There are pretty much no static backup systems that have any lifespan that is worth mentioning so a dynamic system is usually much better.
This is how i've solved it and it's a pretty cheap system in comparison to high-volume tape backups or other solutions. You do not HAVE to go with the most expensive (or fastest) harddrives, the only thing might be that you need to cycle your disks a bit earlier but thats about it.
And at all points you have a minimum of 4 copies of your files. Chances are very slim that all 4 copies gets destroyed at the same time, barring possibly a bombstrike :|
There is an additional solution which right now is a bit too expensive for the volumes needed by most photographers and that is online storage. It's a perfect way to store your business data however, but remember one backup is no backup. You do need multiple backups to cover all angles.
Sorry for the long post but hope it will at least give some ideas that MIGHT save your data in the future
