The Only Thing I Can Suggest Is To Attempt To Undelete The Files... If The NAS Drive(s) Are In A Linux Format, I Would Advise Using A Live CD/USB Distro, And Attempting Recovery That Way...Here's Some Advise From PC Advisor...
'Another drawback with most undelete utilities is that they won’t work with networked storage, i.e. NAS drives. The disk(s) in a NAS drive are under the control of the drive’s own operating system (usually a Linux variant) so software running under Windows isn’t typically able to attempt a recovery. If you’ve accidentally deleted a file it might just be in the NAS drive’s own recycle bin (if enabled) in which case you might be able to recover it, so first check the documentation. If the file is properly deleted, though, there are only two options.
So long as you don’t mind getting to grips with the insides of the NAS drive and your PC, it might be possible to remove the disk(s) from the NAS and attach them directly to your PC. Now it becomes possible to use a Windows undelete utility but with two provisos.
First, your NAS drive might use a different file system from the drive in your PC so you’ll have to check the NAS drive’s documentation to select suitable software. Second, if your NAS drive uses a RAID array, your file might be distributed between more than one physical disk.
Some recovery software is able to handle RAID arrays but, again, you need to bear this in mind in making your selection. If you don’t fancy dismantling your NAS drive and selecting suitable software, the other option is to send your array off to a professional data recovery company.'