Regarding the Fake Barn counterexample to the causal theory of knowing I heard that Gilbert Harman's response is to deny that there are fake barns at all, is this correct? Does anyone have a link to a paper? I can't find a source for this anywhere.
I'm afraid I don't have an answer for you, but perhaps I can offer you a somewhat useful non-answer?
As you know, Harman's major writings on epistemology are three book-length volumes; most principally, his classic Thought from 1973; Change in View: Principles of Reasoning from 1986; and Reasoning, Meaning, and Mind from 1999. (He appears to be on a 13-year schedule, so perhaps something new on the subject will be coming this year.)
The first publication of the Fake Barn Country scenario (that I am aware of, at least) is in Alvin Goldman's 1976 paper "Discrimination and Perceptual Knowledge" (in the Journal of Philosophy, Vol 73, No. 20), which explains why the matter is not raised in Thought. Using Google Books and Amazon search tools on the latter two volumes, I do not see any references there, either.
This means that if Harman did respond to the Fake Barn Country example, he did it in an article. A full bibliography of his writings can be found here; there are a number of post-1976 articles which may (or may not) contain the passage you are looking for, if you care to dig through them all. (I imagine most university libraries would contain most of the journals referenced.)
Having not read Harman's response (if there is one), I cannot comment on his actual views on the matter-- but I can suggest that "denying that there are fake barns at all" does not seem to be a valid response. The Fake Barn Country example stipulates that there are fake barns, so they are clearly there; moreover, it stipulates that the driver is unaware of their presence, so it does no good to argue that "they are not there for him", as this is precisely what is at stake in the argument.
Do you recall where you heard of Harman's (possible) response?
Thanks for your help after much searching I could not find anything. It seems unlikely but perhaps I confused the names Harman and Hetherington as the only possible counter to the Barn example I have found is a paper called Actually Knowing by Stephen Hetherington. It's not completely denying the traditional response but argues that in our interpretation of the case epistemologists commit a counterfactual fallacy. Basically from what I've read; if Henry had turned his car around before seeing any fake barns then Hetherginton argues Henry he might have knowledge.