*SPOILER* Is it just me, or is there a plot hole?

I'm just trying to make sense of Oscar's plan and thoughts, but my reading is that if he lived, the security company would try to investigate further. They would probably look at the footage and other evidence more closely, and possibly examine his wife or Ong's wife if they can connect it.

They would question him to no end and would most likely succumb to their scrutiny. The boss, Buddha, insinuated this notion at the debriefing after Ong's death. With no other evidence, the gambit with the other key and box worked, because it felt like a sufficient explanation for Oscar's actions.

Good movie. It's somewhat like a more lyrical and less outlandish Breaking Bad. Really liked its atmosphere and could feel Oscar and his family's downtrodden plight through the poor Filipino metropolitan setting. The story would work in other cities, so a remake is likely on the horizon. But without the film's immersive use of Manila as its greatest strength, why bother.

I'm with svocchipinti; and of course they eventually would have discovered the old switcharoo on the surveillance tapes but Oscar would be long gone by then spending the money with his family.
Furthermore the switch from an honest hardworking and decent man to a criminal who takes a shot at his boss was a bit too unrealistic for me

I think his theory was, if I die my wife gets all of my personal belongings returned to her, if I am arrested my personal belongings are entered into evidence for the eventual trial. My wife and children need the money today or tomorrow, not 5 years from now.