LogFAQs > #895332842

Good guy overhears how they have to be careful that he never finds out. He angrily confronts them, demanding to know what it is he shouldn't find out about. They proceed to whine about how his surprise party is now ruined. He totally buys it.
If he had just stayed hidden and silent, he could have heard the rest of the conversation. But good guys overhear. Only villains eavesdrop.
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There is no "would of", "should of" or "could of".
There is "would've", "should've" and "could've".