How could someone call one of my contacts without unlocking my phone?

I left my phone in a lecture hall a couple days ago. I went back and couldn't find it. Then, a few hours later, I got an email from the person who found it - apparently they had called the last person I had called (it happened to be my dad), and he had given her my name. From there she looked up my email address in the university directory.

My phone is protected with a screen unlock pattern (fairly complex..). And I know that you can make emergency calls without unlocking the phone. But how did she call the last person I called without unlocking my phone? Did she somehow figure out the unlock pattern (and lie about it)? Or is this an actual feature? For whatever reason, I can't figure out how to do it, which makes me suspicious.

I have a t-mobile mytouch 3g.