I was trying to say the opposite. Or rather, I was actually trying to say that phenomenon are rarely unscientific, only the explanations. You can have scientific and unscientific explanations of the origin of life on Earth.
You really only declare a phenomenon unscientific if we've spent a long time not being able to come up with any good scientific explanations. For instance, we commonly regard the question, "What happened before the Big Bang?" as outside the reach of science. But that's just provisional -- if someone came up with a really great theory that explained the nature of the universe before the Big Bang, and it produced testable predictions, then suddenly the question would in fact be inside the reach of science.
I challenge you to even conceive of what a "test for consciousness" would look like. Let's imagine you have one. How confident in it will you be when the first person who fails it says "but I am conscious!"?
False positive and negative rates are not particularly new to science or medicine. When we run blood tests to determine if a person has a particular disease, some percent of people with the disease will be tested as not having it, and some percentage of people without the disease will be tested as having it. Just because we fail to detect something accurately 100% of the time doesn't mean we don't understand it.
When you are making your magic consciousness detector, how will you know when it is working?
Let's say my theory says that rocks are conscious and hippos are not. Without some means of detecting consciousness this theory is untestable.
That might be going to far. To an electric field an uncharged particle "doesn't exist," but that doesn't actually mean that uncharged particles don't exist. Likewise there could be particles that don't interact with any known force, or even particles that interact with nothing. The right thing to say is that the existence of those things is categorically unknowable, and that studying them may even be a waste of time, but you shouldn't say that they are known not to exist. It's a similar story for consciousness, which is at least purported to interact with things, although the interaction is one-way in the "wrong" direction.
But that isn't what I said, I said that from a scientific perspective there is no meaningful distinction, which is exactly what you're saying. Its existence or lack thereof is irrelevant because it cannot be measured.
Not being able to directly observe something isn't actually a problem. We can't directly observe black holes. We can't directly observe the center of the sun, in the foreseeable future. We can't directly observe the evolution of life on Earth.
But we can use our theories to explain these things to also make predictions that can be observed, tested, and used to discard incorrect hypotheses.
Where science ends is when there are no observations you could make which would disprove your hypothesis. For instance, intelligent design basically says, an intelligent designer could have done things in whatever weird way they are, so any observations are just how it happened.