So I've had this happen twice now. I couldn't find the replay file, the one in My Documents is a few months old.

While Masquerade is on it's possible for names to get swapped. I've experienced this twice now, I've only seen it since the change that the winner is shown in chat.

After I bought out the last player it would say that someone else won the game. I assume it's the last player to be bought out, but I can't verify that. The players didn't join the next game so I couldn't ask them. I went to watch the replay and my name would be on someone else's HQ entirely since the game start. So something is a bit messed up there.