Unfortunately for the theologian, your statement here is correct. In order to say something is miraculous (a form of supernatural) we must have a method of differentiating that which can occur naturally vs that which cannot. Metaphysically, one cannot say “this cannot occur naturally” as it would require omniscience of nature. We can “infer” certain things cannot occur naturally (resurrections, limbs regrowing, etc.) but we could never say “this could not have occurred naturally and is therefore supernatural”. Otherwise it’s all just inference and whenever these supernatural inferences CAN be investigated we find that the reasons for the event can be explained naturally.
I see no other logical method of concluding things on a supernaturalistic basis as these inferences can easily lead to mutually exclusive supernaturalistic conclusions and is therefore an unreliable epistemology.
Ex. we found a heart cell in this host…therefore Jesus wants us to know he is present in this church VS we found a heart cell in this host…therefore we know Loki is playing a trick on the Catholics
We just have no way of dis/confirming that the conclusion we have come to based on “the unexplained natural event” equals a confirmation for the God we already accepted to exist.