That is a valid theory. Except There have only been a hand full of requests for God
to immediately step in and handle a crisis. And the response has been 100%.
So confirmation bias is ruled out.
No, it isn't. Indeed, the fact that you can only think of a few times when you made these requests actually strengthens the likelihood that it's confirmation bias on your part rather than a legitimate actor working on your behalf. For example, you could easily have rationalized something that seemed crisis-like down to something more manageable that you could (and did) handle on your own when your prayer wasn't granted without being aware that you were even doing it. This is how the human mind operates. Things that seemed far more critical and important to me when I was younger (or even a few weeks ago) dwindle in importance over time. Eventually, they drop completely off the radar - matching my revised expectations of their importance, after the fact. I'm not at all surprised that you don't remember them - as I said, this happens subconsciously unless you make a deliberate effort to get around it (say, by recording every event as it happens in a way that isn't subject to fallible human memory)
I was playing a tabletop RPG a few weeks ago, and I rolled a natural 20 (instant critical hit) - and then rolled another natural 20 to confirm it. You can be sure I'll be remembering that one for a long time. But I couldn't tell you the results of most of the other rolls, except a general feeling that I wasn't especially lucky. Give me a few months, and the only thing I'll remember out of that session is that pair of 20s.
There are PLENTY of times I've prayed for green traffic lights so I could get to an
appointment on time. I've never taken those prayers seriously and would not count
any such frivolous requests, even thought the "results" seem to be on the high side.
That I would attribute to confirmation bias.
Did you actually read the page on confirmation bias? Confirmation bias is when your subconscious adjusts your expectations of reality to match what you thought should have happened with what actually happened. As you just said, you wouldn't expect such frivolous prayers to be answered in the first place, so there was no need for confirmation bias to wipe away the discrepancy when they didn't actually happen.
Some stories I've read were that "God woke me up in the middle of the night to come help you cross the river during the snowstorm." Such stories helped my come to my current conclusions.
I don't think that reaches the "physical" threshold you mentioned though.
But it does illustrate confirmation bias, since I seriously doubt those people remember all the other times they woke up in the middle of the night when nothing special was happening. People remember the times that stand out and forget the ones that don't.
Anyway, to address the other point, it doesn't matter whether it's minor or major. If God does something, it leaves behind traces that could be detected. And that completely leaves aside the problem that comes as a result of picking examples like that - you're making God essentially powerless to do practically anything unless a believer does it for him (more to the point, does it with only their own abilities - so much for miracles such as divine healing, turning water to wine, and magically multiplying food to feed a giant crowd!), in order to avoid the thorny issue of explaining why he doesn't leave traces of himself behind that could be picked up. And that flat-out ignores all the times that people attribute some event to God - not some believer doing it for him, but God actually doing something in the world.