Calling my mom in a location she'd never been to

I was young but old enough to be home by myself. Maybe 10-12 years old. For some reason, maybe someone had called, but I needed to get an important message to my mother, who worked at local college. She had a couple phone numbers in which to call her. Her personal office and her department office. I called both, no answer from the first and nobody could find her at the second. The phone numbers at her college all had the same first 4 digits and the last 3 were different. For some reason I urgently needed to give this message to her and could not get a hold of her. I went to her address book, which had some other numbers from the college jotted down, but with info about where they connected to. Assuming my mother wrote these down because she knew the people at the other end, I thought i'd give them a call and ask if they had seen her. I called the first two and they weren't anything slightly related to what she did at her job, but seeing from the first 4 digits they were connected to the college. Finally, I called the last number, it connected me to someone who explained I had called a sheet music library room somewhere on campus. My mom teaches English, but being 12 and having seen the number in her phone book it made sense to ask. So when I asked for my mom the man on the other end said strangely "uh....hold on.. yea.." He turned the phone over to my mother. She immediately asked me how I was able to track her down to this music library. She had never been to this place and decided to stop in randomly at the time I called. I told her that I had found the number in her phone book, she explained that she had mistakenly written down the last few digits trying to connect to another number.