@qwerty4321 Hi apologies for the late reply. The bug that you mention is something that I have seen in older versions actually and it was allegedly fixed in this version (as a consequence related reports stopped coming), however in this case it seems the culprit was Win 10 along the AV.
Windows 10 has a problematic behavior regarding permissions for apps that are not verified, and antivirus can become troublesome for files that are seen as modifying the system, as such the anti-virus real-time shield could have messed up the saving procedure silently at any given time and unfortunately it’s an actual danger that we have verified, even if it’s really rare to occur. To improve your use of Pencil2D under a Windows 10 environment please read this guide as well:
The problem with such issue is that if you lost the files for whatever reason at some point where you didn’t notice, and you saved over the same file with the blank frames, it means you overwrote your file with new data reflecting the current behavior.
In that case I’m sorry to say that if the file was not corrupted but rather you kept saving over it in such state your drawings are simply gone 
Honestly this kind of cases is why we try to frequently tell users to never save over the same file for large projects over an extended period of time, this isn’t even a Pencil2D issue but a general work habit due to murphy’s law.
One must always make extra backup copies instead of relying on a single file. I’ve had my own problems with Animate CC in this front recently, where an animator in my crew saved a humongous file collecting about 10 shots, he kept working on it, and lost 2 weeks of pro work before a due date because Animate CC spazzed and deleted all his workspace configuration and corrupted the long file, and since he didn’t take countermeasures, he had to start over again (and I had to carry his work as well to make it in time). This just goes to show that regardless of the software this kind of things do happen and we can only prepare ourselves.
That said, not all might be lost, please take a look at the guide below and look in the Experimental Recovery section. Maybe using a third party app to recover your files in the temporary folder might help, even if a bit, but you need to be quick before the files in the hard drive are overwritten (this happens automatically whether you want it or not due to how Windows manages the files in %TEMP%).
You can also look at the File Backup section to enable per-file recovery similar to macOSX Time machine feature.
While it’s not warranted to find all the images if too much time has passed, it may help recover a few of them. On the other hand please look for any extra copies you might have made before.