It's said that when a functionary in India nods his head to the side and says "No problem" you know you have a problem.
In his Brazilian travelogue In Southern Light, Alex Shoumatoff gives a Borgesian rundown on why this may be the case.
This has been a common problem for Westerners trying to get information not only in the Amazon but all over the non-Western world, where the local people often tell visitors that the object of their quest exists when it doesn't. Among the reasons are: politeness, reluctance to be the bearer of disappointing news or the source of unpleasantness, unwillingness to confess to ignorance about the subject, failure to understand the question, desire for reward, desire to keep the visitor and his goods in the vicinity, desire to get rid of the troublesome visitor by sending him somewhere else, desire to protect oneself or something or somebody else, belief that the misinformation (obtained from somebody else) is correct, laziness (saying yes because the truth is too complicated to go into), indifference, different outlook on the subject, different outlook on what is true and real.
Shoumatoff produced this epistemology of no worries while writing about the legend of a tribe of women warriors who live without men. The legend originated in the ancient Mediterranean and somehow became associated with the South American interior, giving the Amazon its name. In search of these women the Spanish conquistadors were known to enslave, torture and kill their informants much as they did in search of the golden city of El Dorado.
But you can remove the references to "Western" and "non-Western" and insert any two groups in which one wields more power than the other (parents and children, sysadmins and users, customers and clerks or clerks and customers, etc.) and see the same result.