That's a different prediction.
No one has been able to come up with a plausible test for whether a biological object was designed. It is likely that no such test exists. We can look for human artifacts because we know all sorts of things about humans already. But looking for evidence of a designer, having no knowledge at all of what the designer might be, is a different kettle of fish.
1) Look for evidence of communication, interaction with a designer.
2) Look for evidence of spontaneous genesis in non-unique multiple dispersed closed environments. (stuff appearing in 1 mud puddle when thousands of equivalent mud puddles exist).
3) Look for evidence of mistakes, or failures. (entrons)
I believe evidence exists for each of the above.
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4) Look for evidence of uniquely defined fixed constants for values that should otherwise, naturally, be highly variable. The coupling constant, alpha, for instance that Feynman suggests must have been defined by God. (among a dozen other such constants)
On what grounds do you think it's likely or unlikely that no such test exists? Is it intuition, because you assume they are wrong, or because you have some evidence that no such test exists? Is there any reason why people shouldn't try to come up with such a test?
We can look for human artifacts because we know all sorts of things about humans already. But looking for evidence of a designer, having no knowledge at all of what the designer might be, is a different kettle of fish.
I don't think that's true. Looking at the fire pit, for example, it is just as useful to know what a natural fire leaves behind as it is to know what a man made fire leaves behind. If you only knew what a natural fire looked like, it would be possible to determine that a fire didn't look natural.
As a semi-made up example, suppose natural fires are started by lightning and lightning very rarely strikes twice in the same place. If I come upon the remains of a fire that contains many layers of strata suggesting there were many different fires in the same place, I could simply assume that this spot was a random fluke of probability or I might start looking for another reason why there were repeated fires in the same spot and look to make sure that I'm interpreting my evidence correctly. At that point, random chance, some other natural mechanism for starting fires, or even the hand of a fire builder all become reasonable alternative explanations that are all tested, just like ID, by looking for characteristics that distinguish the natural from the deliberate. And what's important to note here is that the person who insists that random lightning strikes started all fires before a certain period of history can always claim, without proof, that any fire was random but that's not necessarily the correct conclusion if some other agent or process was really at work. Just because something is possible does not mean it was probable or even correct.
Archaeology is full of alternate interpretations for the same evidence when it's inconclusive. And as with other fields of science, those interpretations are often biased by the assumptions of the researcher. For example, an archaeologist that accepts the Clovis theory of human migration into the Americas will be inclined to look at an inconclusive fire pit and see evidence of a natural fire while a an archaeologist who believes that the Americas had a pre-Clovis population might be more inclined to see it as evidence of a pro-Clovis population. The evidence doesn't prove either one right, but neither are they being unreasonable in their interpretations.