I had been working on an animation all day yesterday and when I opened the same fla today, all of the work had been deleted and the only things remaining were sketches from before I started working. I had been saving the fla yesterday and made sure it was saved before closing. I'm not sure what to do now. I already checked the recovery file and its the exact same issue.
It's Mac specific, but the TMP folder for Animate excists on both platforms. It's a matter of locating it and then going through the FLA files that are there.
The next time you continued some work, try saving the FLA to a different location after making only a few changes. Restart and open the FLA to see if the changes are there as expected. Assuming so, save the FLA back to the orignal location.
I'd also run hardware diagonostics just to make sure there's not some hardware based issue (usually stroage media related) going on.