Q: What happens when I reveal Shadow of the Past and my nemesis minion has the same title as an enemy in play?

A: Your nemesis minion cannot enter the game in this instance, so it will remain set-aside and does not enter the game. However, you still reveal your nemesis' side scheme and shuffle the rest of your nemesis's set into the encounter deck. This will cause Shadow of the Past to gain surge as dictated by the card. -(Official FAQ)