It seems like a bug is a definite possibility; that the game generated the heroic version instead of the normal one.
Let's suppose, however, it was not a bug, but rather a statistical outlier, like a lottery win, or an honest politician; I hardly think that qualifies as "out of control"; if one out of every 100 people had that type of luck, it wouldn't exactly be a game breaking issue, especially when you consider that the only time random luck like that can affect anyone else's play is if one group somehow all managed to get that lucky at the same time and gain a huge gear advantage. Given the nature of probability, this seems rather unlikely.
My 30 copper is on a bug; if I'm wrong send in-game email to collect your bounty of riches XD