First, let me say I'm sorry to hear you've lost data - this is never a fun thing. I can't overstate the value of backups!
fSekrit 1.2 is a pretty old version, and embarrassingly
enough, 100%-safe saves wasn't implemented until the latest version, 1.4. Under normal
situations, earlier versions shouldn't experience data-loss, unfortunately real-life has abnormal situations
. All versions previous to 1.4 saves directly to your executable, which means a crash, network failure, pesky antivirus application, (...) can cause the save to fail, and our old data being overwritten. Newer versions save to a temporary file first, and only overwrite the original once the temporary file is fully saved.
If you haven't modified any files on the flash card since the failed save, there's a possibility you might be able to restore the truncated data - it's a bit of a far shot, but it might
be possible... it would probably require a raw dump of the flash card and some custom search-for-container code. How big is the flash card, and how sensitive is any non-encrypted data on it?
I'll continue this in e-mail, but posting here to show that an issue like this is indeed taken serious.