Amazon Engineering interview questions

I was contacted via email by a recruiter. She expressed interest in me as a candidate to work in one of Amazon's software development groups. I expressed interest, and she arranged for a phone screen with a developer. Now, I little bit about where I'm coming from: I have been the interviewer for a couple dozen phone screens and been an in-person interviewer for somewhere north of a hundred more. I know the give-and-take process, and I know that the interviewer is looking for thought process as much or more than conclusion and a good candidate clarifies the problem by asking questions. The problem with my interview is that I think the interviewer was out of his depth. THere was nothing wrong with the style of question he asked, but he was not prepared to answer questions I asked meant to explore the problem space: such as "what is the input format?" or "is performance a factor?" He also seemed to have difficulty grasping the solution I was proposing. Now, I can't tell you whether ultimately I had a correct or incorrect solution. But that's not my point. The issue was that he was not able to follow my solution at all. I think he had a specific solution in mind, and so had dfficulty switching his way of thinking to alternative solutions.