My sympathies. To my knowledge though, saves are local - I don't see how someone external could have wiped the data. Please correct me if I'm wrong because I would hate to run into this myself.
Maybe consider backing up your save file in the future to avoid anything like this? I've yet to play Hero's Guild but I know that many indie devs, especially in early pre-release versions make changes which for some reason render old saves incompatible (I'm not a dev, I don't know what type of change would necessitate that) and sometimes choose to delete the current saved game upon installation of a new version which requires it.
Again, doesn't sound like that's what happened here, but just an anecdote as to why it's always a good idea to back up your saves.