While I'm not in any way an expert in simulation making, wouldn't it seem just a bit too convenient that, in all the monstrous computing power behind making the universe run, the Overlords couldn't devise a pretty clever and powerful algorithm that would have found us already? Maybe you can help me see why there would only be a crude algorithm that superintelligences should fear being caught by, and why they wouldn't have considered themselves caught already.

Apart from this, I'm in agreement with other commenters that a stronger argument is the vastness of space.