If my car disappears from my garage, it may be because it was stolen, or maybe because it was transported to an alien planet by extra-terrestrial life forms.
My assertion that it was E.T. does not mean that your counter-assertion that it was stolen is true. Maybe I lent it to a friend and forgot, or my wife took it to be pimped out on Overhaulin', or that it was repossessed due to some bank error.
It's quite appropriate to raise additional possible explanations. It's quite inappropriate to tell someone that their treatment is in no way causative to the amelioration of symptoms, especially when they cannot know for certain that they were not.