Change Blindness:It's your inability to notice changes that happen right in front of you, even if they're hugely obvious... as long as you don't see the actual change take place.
Cryptomnesia: You come up with a great idea. But it isn't yours, your brain just doesn't bother remembering where it got the idea. It's a form of plagiarism disguised as epiphany. So if you were "blind to the miraculous", you might think it was your idea that people with shellfish allergies shouldn't eat lobster, instead of God commanding you not to eat it (Leviticus 11:12)
Saccadic Masking: Quick, look at the wall to your left. When you flicked your eyes over there, for just a moment, you were blind. And you didn't even know it. Your optic nerve shuts down while you move your eye so you don't experience motion sickness.
Subconscious Behavior: Our brains are lots of things, but they aren't particularly aren't good at coping with entirely unexpected situations. We deal with almost everything that happens to us by comparing ongoing events with past experiences, mostly in our subconscious. Our minds pay much more attention to comparisons with past experiences than they do with the events facing you at any given moment. Seeing something truly miraculous just might cause you to think you were simply hallucinating, or daydreaming.
(This one is kind of a stretch) Proprioception: It's your brain's map of your body. Your mind can be tricked regarding its own size, and even sensation, like when you press your arms against a door frame for several minutes and then step away, only to have a "mysterious force" lift your arms. If a deity naturally altered it's surroundings due to it's nature, and you were change blind to it, you might stub your toe on one and your brain would simply re-adjust to thinking it hit a coffee table.
That's without going into emotional explanations. There is the possibility that, paraphrasing the movie Se7en, you can't just "walk up to someone and have a conversation with them. You have to hit them with a sledgehammer, and then you'll notice you have their full attention."
If there are gods, then there exists the possibility of demons, who would trick our minds more effectively than the everyday brainwashing we already get. How easy would it be for a super-natured being, given extreme longevity, to alter fundamentally how we "see" the world around us? Even from a cultural standpoint, going back far enough when there were few humans, to develop what we know as a cargo cult, but one on a massive scale with misinformation (religions, atheism, etc) at its core.
Combined with the fact that if a being was around long enough, and was different enough (or so similar to us), we wouldn't even be able to recognize it was a god. It may look like
a rock, or a tree, or just about anything.
I don't worry too much about those things, but i do find them entertaining.
Be careful of who you may be entertaining, for you may be entertaining.....