Now that the situation probably won't present itself again, and I feel a teeny-weeny amount of remorse about it, I must admit:
Before the days of cell phones and GPS systems, I'd often stop at a phone booth (Do they still have these?) to check the directory for whatever information I needed. If I found what I was looking for, I'd rip the page out of the book, rather than write it down.
There, I've said it.
I did this today to my own yellow pages at home, because I was without pen and too lazy to get the book out again and look up the number. That's when I realized that this behavior could annoy my fellow man.