Here’s a rescue:
You are not expected to know the answers to every question in the universe (the answer to the question about life, the universe and everything is, of course, 42…).
Your objective is to know the answers to just enough questions to be perceived as competent and credible. Your responsibility – and the expectation on the part of the customer – is to be the conduit of answers (of questions that you don’t know how to answer) back to your customers, later on. Post meeting, your job is to access the appropriate resources to get those answers and then deliver the answers back to your customers.
The use of “Parking Lots” in managing questions is an excellent approach in managing and tracking questions (and answers). Many Great Demo! practitioners use a Word document to capture questions – and then use strike-through text to show questions that have been adequately addressed in a session, leaving the unanswered questions in normal text. This provides a written record of what was addressed in a demo meeting or Discover session and what remains open. Very elegant!