Can you detail the dupe? Not allowed here? I have no interest in doing this, just wondering what the hell happened exactly. Also opiate I can't believe you are still playing!!! You have more patience than I.
It's already gone, so there's no harm.
There was a buffer overrun on the RMAH. In short, if you put up in excess of 1.7B gold to sell for money, then canceled that auction, the money came back 2x the original amount.
Put up 2B gold to sell on RMAH, cancel, now have 4B gold. Put up 4B gold, come back with 8B. Put up 8B, come back with 16B. Continue repeating until satisfied. You could literally double your money in about 10 seconds, over and over.