Same thing happened to me!
Sent a ticket with regards to this under Issue ID: #71245534
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Hey there Nicholas!
Game Master Vyhexus here, believer of valor, victory and vitality! Well met ٩(◕‿◕)۶
Thanks for getting back to us on this!
I entirely understand the frustration which you feel, as I’ve lost save game progress many a time before (with both Blizzard games and non-Blizzard games)…it feels like a ritual that all gamers have to go through at least a few times >_<
That said, with regards to your Warcraft III: Reforged situation here, I’m afraid Game Masters have incredibly limited tools or utilities to assist with this, which is why the previous Game Master has suggested you report this to the game development team over on the forums, as they will be the best-equipped to find a solution to this 
In terms of restarting, I know that initially it feels very troublesome to embark on a journey you were already halfway on, but trust me when I say once you begin, you’ll get into the groove of it in no time. After all, that’s why many of us play the same games over and over again (the amount of hours I’ve spent in Diablo II & III…)!
I know this isn’t the result you were looking for today, and trust me when I say that I wish there was more I could do to help you with the situation you face. It’s our commitment to provide an epic experience to our players, regardless of the outcome, and I hope you can understand that we’ll always strive towards that, no matter what!
Have a fantastic time with friends and family, full of fun, laughter and fond memories 
-V
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This was the response by the GM!
Long story short;
- They can’t do anything about it
- You have to replay from the very beginning!
- All the achievement / portrait which you’ve unlocked is all gone!
- There’s no guarantee that this won’t happen again in the future!
So basically;
- Don’t play till this issue is resolved -_-
- This happened because it’s the dev’s fault but sorry, nothing can be done and no compensation nor solution will be given. Sucks to be you :), but you’re always welcome to re-play from the very beginning again (though no guarantee that your progress wont get wiped once again).