I'd be really surprised if this information was stored anywhere. For example, the registry will store information about FME and its installation and settings, but not anything related to individual workspaces or their contents.
FME doesn't write translation files to the installation folder. However it does write to a temporary folder during translation. If the hard drive happened to crash at the same time that the workspace was being run, then you might find something in the temp folder. The temp folder can vary, but Workbench reports my "Current working folder is `C:\Users\imark\AppData\Local\Temp'"
So take a look there. You generally get a copy of the workspace and (possibly) the log file in there. Look for files starting "wb-". But these are called temporary for a reason: FME cleans up after the process is complete, leaving only your original workspace and log file.
In short, if you can't access the original files - and you don't have a copy on an FME Server repository - then I think you are out of luck. Sorry I can't be the bearer of better news.