Wouldn't surprise me to find one hanging around somewhere in the basement (not hooked up of course). You find all kinds of old random things in these farm houses. The real fun begins when you get into the electrical wiring.
Documentation is huge. Unfortunately, just about everyone around here hears the word and goes "oh yea, I've got it all documented, right here" while pointing to their head. Doing that is great for customer retention but boy does it make it hell for the next guy. I try to document as much as I can and copy in the customer to it, but there's some cases, like this one, where the map of the phone lines will have a couple of circles with "???" inside of them.