I'm new to hosting servers with minehut and stuff, but a few things came to my mind about how this happened:
1) You may have accidentally clicked on "Reset Server" in the Danger Zone in the Dashboard of your server thinking it'd just close and reopen your server instead of actually clicking the "restart" button at the side of "stop". Happened to me a while ago, so maybe this happened to you too.
2) Someone may have pass-guessed your account, went into the dashboard, and reset your server. This is probably NOT what happened, but it could be possible.
3) A bug. Yes, a bug. Even though Minecraft doesn't have that many bugs, there definitely are some gamebreaking ones out there that nobody knows about.
4) [This is probably not possible but since I'm new to Minehut I have no idea if this is possible or not.] Maybe you gave admin to a minehut user to access your dashboard and servers?? I don't think this even is possible but who knows.
That's everything I can think of. I hope this helped you I guess.
(Please forgive my bad english spanish is my first language)