Well, I guess that we have look at things rather differently. To me, using the term "idiotic" is unnecessarily disparaging of the agent. The answer may have been unconvincing, dubious, probably erroneous, etc... I suspect that if I had been in your shoes at the receiving end of such a call, I would have doubted the validity of the literal statement too but would have taken its core message, namely that they do not have the information you were looking for and would not have concluded from this that the agent was an idiot.
I can quite see how an agent, put on the spot to come up with an answer to unusual questions that must have felt strange to him/her, might have come up with something like that which, while erroneous from a literal perspective, nonetheless conveys the more important truth, namely that they do not have the information you requested.