Go to your backup - You don't have a backup? That's why you should keep a backup of "important files", and TWO BACKUPS of PITA to recreate documents like thesis and legal/financials. Keep these in two physically different locations. If you have a fire or a break-in and all your backups are together. . .
You might be able to recover this with professional (aka expensive) recovery software. I've had good luck with Data Rescue 3 (I don't work for them, don't get any renumeration for mentioning them).
Worst case scenario... you'll have to engage a professional to put the chip on another device, or recover the data.
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