Hi, @lostdata. I’ve had this happen before, too.
Any chance you’ve deleted a copy of this TiddlyWiki before and have a previous version sitting in your Recycle Bin you could recover?
Do you have any sort of automated backup running on that machine? Time Machine, Acronis, Norton Ghost, or anything like that? (I’m guessing not, or you’d have mentioned that already — but it’s always worth asking in case there’s something you haven’t thought of.)
If the TiddlyWiki was saved in your Dropbox, Google Drive, Box, or OneDrive folder, you may be able to log onto that service’s Web site, find the 0-byte version of the file, and click to see if your cloud storage service has a previous version available. (Most of the services nowadays keep at least one previous version, I believe.)
You may be able to right-click on the 0-byte file and view Properties » Previous Versions (tab). If Windows is preserving version backups, there might be something there.
In the absence of that, I might try the free version of Recuva:
… which you can put on a USB drive and point toward the directory where your TiddlyWiki was saved. It may be able to recover a version of it, especially if you haven’t done much computing since the error occurred.