Best
DOUG: Hmm, I'm curious if Joe can make a 3:30 seminar.
When is Joe's flight due in?
YOU: 3 PM. ... What's the seminar?
When you ask someone a question out of nowhere, even a simple, factual question, they will immediately wonder why. It's what we do. Since you want information from them, throw them a bone and give a phrase-length preface to why you want the information.