I had the same problem. I lost a profile with a fully complete war-mage, almost complete nightmare section, too. I posted a question about it on Robot's forums yesterday, no response yet.
It's no small irony that the first time I lose an entire game's save-state, it's due to some bug in a cloud service designed to prevent such things. I find it pretty hard to believe there's no local storage as a backup, but there doesn't seem to be.
 Looks like I was wrong about local storage. Over on the Robot forums, one of their guys posted this:
If you're looking for the location of the profiles on your hard drive it's in.
[Location you installed Steam to]\Userdate\[SteamID]\102600\remote and the file is called Profiles.xml
So on my machine it's D:\Steam\userdata\33656751\102600
Thankfully, I use Blackblaze, which keeps multiple days of file versions, so I was able to step back and recover my missing profile from a few days ago.
I realize this doesn't help actual recovery if you don't have your own backups, but in case you do, it's useful information!