Well, if your partition was lost, then perhaps your 40GB chunk of TrueCrypt data was also compromised on the same event...
A hand-made solution:
You could write a script that: mount
your mirror image with an offset, as if it were a partition, then calls TrueCrypt with all the appropriate parameters and your password, then if TrueCrypt returns 0, stop and you are happy, otherwise try again with the next offset, until it has tried all the image.
Experiment:
If the above doesn't work, you should do the following test. Reproduce the same problem with a new hard disk (create an encrypted partition then delete MBR), and try the same approach there. If it works, then probably your chunk of data has been compromised, it it doesn't, then either my approach or your implementation has a flaw.
Plausible deniability says it's gone. – Fiasco Labs – 2013-09-07T05:10:29.073