If the file name is too long for Windows 10, no error message is generated but the file is not saved.

Interestingly, the thumbnail on the Home page for AI shows the final version of the artwork, but clicking on it opens the last one actually saved instead. I didn't know what had happened and closed/reopened AI to get AI to open the correct file, then saw the file did not actually exist.

I was able to recover my work because the last 3 tmp files were not removed, so I renamed the extensions to "ai" and got my work back.

Solution: Please inform the user when the file is not actually saved so the name can be shortened to a legal length.