Yes, the "blank stare" is common and irritating. In defense of doctors, though, they have to deal with alot of people who research symptoms on the internet without any sense of background or perspective. The blank stare may be the doctor's way of saying: "I hear you but what you describe is not a concern, despite the fact that a google search might tell you otherwise. I have seen lots of patients and have lots of experience; you have simply done a google search."
And what the searches produce! Other than Medline, etc., a Google search of some medical topic produces valid, peer-reviewed literature, the ravings of fringe medicine advocates, and endless ads for herbal supplements, fake "Viagra", quack remedies, Canadian prescription outlets, and the usual Searchbot, "Buy your _Pneumonia Symptoms_ on EBay!" garbage.
Yes, in some cases, the Blank Stare may mean, "I am an idiot and am dumbstruck".
But usually it means "I am tired of listening to idiots", or "Not this again".