Picture this scenario. A patient comes to the doctor complaining about back pain. The doctor goes through all possible tests, but cannot see anything. Yet the back pain is real to the patient, even though the best technology cannot see it.
In the case of the back pain, we may not be able to see it from the outside, so we can satisfy the easiest level of proof. Proof will require climbing inside the other person's skin and experiencing what they experience to make sure this is not a trick. But this is beyond the state of the art.
We can't see this back pain from the outside, yet it appears to exist, without tangible proof, using the methods of science. Still the doctors, to be safe, may give the person pain killers, less technical limitations, result in the wrong diagnosis.