What's that?

A few months ago, I had locked myself out of my classroom and needed to get a security guard at my school to open the door. It was early in the morning, and I was still recovering from the evil sound of my alarm clock earlier in the morning. My brain wasn't quite working at its full capability. The security guard arrived with the key a few minutes later and began to say something to me in Chinese. Still in my early morning stupor, I told him I didn't understand. He then began to speak LOUDER. Once that didn't work, he took his left hand out, and began to write Chinese characters with his right hand pointer finger. I still told him I didn't understand. Exasperated, he unlocked my door and walked away.
Two things struck me...first, when I didn't understand what he was saying, he spoke louder. Its funny to me because apparently thats a universal reaction in communication when the other person is having trouble understanding. I'll just say the same thing louder, and then they will get it.
Also, most Western people who learn Chinese learn it orally, and not the written language, as it requires memorizing over 10000 characters and learning how to write them properly. Its a headache most Westerners avoid like the plague. Or bad street meat.
So that fact that the security guard thought I would know the much more difficult written language, even though I clearly didn't know the oral language, struck me as incredibly hopeful and optimistic. I honestly felt bad that I didn't know the written language, as I felt I let him down.