How on earth is it gone?
Failed hard drive? There are great data recovery options for that.
Accidentally deleted from the cloud? Are their local copies on any of your devices? Does the cloud keep older versions / deleted files around for 30 days (like Dropbox)?
Are there any back up hard drives that were used? Can you find any flash drives or SD cards that may have been used to move the files around?
I can’t imagine how it would just disappear, unless you had equipment stolen or physically destroyed…
If that’s really the end of those files, that really sucks man, especially if you were very far along. :\ I had a similar experience when I first started making games and my good old Windows ME (eww) stopped booting right before I left on a family trip.
Just know that the skills and knowledge you got are still there and very durable, which means everything will be faster and easier the second time around, and now you know to keep several isolated backups so that this’ll never happen to you again.