If there's one thing I've learned at my job on a help desk, it's that everyone feels like top dog.
Everyone wants their issue resolved yesterday, and everyone's issue is more important than everone else's. It doesn't matter who they are, if the're comming to you trying to gain access, they're just like anyone else who would come with the same request, and you have all the same procedures to follow rather they're a grad student trying to finish for finals or a freshman who walked in for the first time last week. Nowhere is that more paramount than when dealing with security such as that verification. If you let one person slip through the cracks on security, that's all that would be needed for them to completely ger revenge for having access revoked. (how can you prove that did or did not happen, after all)
I've had to play a brick wall more than once because a security check failed. If that check failed, it may be e fluke, sure. Or there may also be a good reason that you're not aware of. Personally, I hate having to give a customer the third degree for a password reset. I wish sometimes I could wave a magic wand for them and make everything just know them and work. As much as I hate security, I believe in it whole-heartedly. It has to be there, and serves a purpose, and when you're the agent of it, sometimes you have to become a brick wall and not allow access. If they don't like that, get irate and go crying to your superiors about you, that's their problem. If you did your job then you don't have anything to worry about, and they'll get the same thing fron your supervisor as they got from you.
Don't let them intimidate you and make you crack. based on what I've read here, you did well.