I've been working with Adobe Animate for several years and even teach courses in the software- I've never had a problem like this happen before.
A couple of months ago in my Animation Basics calss, a student told me her file had disappeared. There are all kinds of ways people can misplace files, however this one had literally disappeared. I opened Animate and attempted to access the .fla through the "Open Recent" queue and when I selected the file- I recieved an error saying that the file no longer existed (no error code, just the error), and it removed itself from the queue.
Note that this file was created locally on a recently updated, fairly new mac desktop computer. Students are working locally on their files, they don't bring in USBs. The computers are shut down every day, however none of them are set to wipe themselves. Her and several others over the course of the next two weeks randomly encountered the same issue on several different computers, all different files- only with the Adobe Animate software.
I myself just encountered the same issue twice on my new MacBook Pro. Fortunately I had a backup saved on Dropbox- which has strangely felt more safe than saving my files locally? The last animate document I had open deleted itself while I was working in it. I got an error message saying:
The file path, followed by
"The file associated with this document has been moved or deleted outside of Animate. You may want to resave the document before continuing."
-even though I hadn't moved or deleted the file at all. So at least I could create a new save file before it disappeared like the others.
So... if this has been happening to anyone else or if anyone out there has some suggestion or solution, I'd greatly appreciate it. I'm guessing it must be some kind of saving error or more unlikely a virus- it would be strange to target Animat files in particular. In the meantime I'm just going to backup every local Animate file to Dropbox (Google Drive works just as well). I would suggest others who have encountered this do the same.