This is interesting, can you share the encrypted external drive technology name? Is the drive NTFS or FAT?
Also, the logs do not contain any references to save on 27th, how did you save, Ctrl-S? Was there any perceived time for the modified file marker (*) to disappear? Did you Save As, or renamed the file externally?
The copy.xd I referenced was the basis of an autorecovery, but since you didn't crashed, it didnt have any other dirty artboards saved along, it was a far shot.
For additional debugging, can you export last 7 days from Event Viewer's Windows Logs/Application?
Let me know if you need guidance with that.
Thanks!
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Vlad
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