After years of working, many people have been conditioned to think that you always need to know the answers - that conditioning is wrong. One of the things I quickly learned when I was a Sales Engineer was that there would never be a day that I had all of the answers, and if I tried to fake my way through it, customers could see right through me.
I can remember the exact meeting when a customer called me out for making up an answer, even if it was one that seemed plausible to me. To them, they viewed it as an outright lie, since I didn't know for certain that what I was saying was the case. It turned out, after some research, that I was correct - but the imprint of that meeting forever lives in my brain.
We no longer live in an age where rote memorization of facts is important, particularly because we all walk around with supercomputers in our pockets. In fact, I hope that before my son is in school that curriculums update to move away from standardized testing and rote memorization, to a method of learning that focuses on working with information that is easily made available.
What is important is knowing how to find, distill, and work with all of the information that is at our fingertips. We all need to be able to figure out what is fact, fiction, and outright dis-information. We need to know the rough concepts rather than most of the details. When there comes a time to dig into the details, then you can worry about those things.
So the next time you're in a meeting at work (or even in an interview!) and you don't have the answer, just say "I don't know, but I'll find out and follow up with you." It's simple, it's to the point, and you still end up getting the information to the person that asked.