I agree with what others have said, he is the one who reacted poorly and didn't make the space for you to relay your questions. I can definitely relate to going into a situation like this feeling confident and prepared and having it all fall to pieces once I start speaking. But it happens and you learn to move on. If you're still interested in him after this, could you get his email address from your dad or online? You don't owe him an explanation but perhaps you could send a "hello, we met the other day and I didn't quite get the chance to go over some of my questions. I would love to ask you about xyz..." You've already made your first impression, but it would let him see that you are genuinely interested in the field and are making a real effort, and he can read your thoughts as you intended them to be. If he doesn't respond or is rude again then he's not worth your time anyway! Don't give up!