One of the stock objections to Christian theism is the claim that if God existed, he’d prevent many of the (allegedly) gratuitous evils we see in the world around us.
But other issues to one side, this speculation raises an intriguing conundrum. Most of us have grown up on science fiction stories–in books, movies, and TV dramas. One popular SF plot involves time travel. A catastrophe in the recent past has blighted human existence. It’s too late to undo the damage, but it’s not too early to undo the damage. The protagonist travels back in time to a time before the catastrophe, to prevent it.
However, a paradoxical effect of his mission is that, if successful, changing the timeline will instantly and utterly erase the record of the previous timeline. No one will remember the catastrophe he averted. Even he won’t remember what he did, for the counterpart who went back in time doesn’t exist in the new timeline that takes the place of the old timeline. He saves the world, but he gets no credit of his feat.
By analogy, for each (allegedly) gratuitous evil that God prevents, there will be no historical record of his intervention (or contravention). So, for all the infidel knows, God has, in fact, preempted many (allegedly) gratuitous evils. In the nature of the case, doing so will leave no trace of the preempted evil.