From the log of that game, it looks like you had a 2/5 opening, so you did nothing on turn 1 and drew the 5 Copper for turn 2. On turn 2 you played 5 Coppers to buy Mountebank, then discarded everything, shuffled your deck and by shuffle luck drew again 5 Coppers for turn 3.
So don't forget turn 1, even you didn't do anything in it.