Dear Cable/Phone Jack Installer Guy,
First off, I would just like to say that I'm sorry for not addressing you by your proper name. It's just that you never introduced yourself formally, and you keep calling me ma'am, so I've created you a pseudonym of Cable/Phone Jack Installer Guy.
With that being said, the real purpose of this letter is to let you know that you shouldn't worry too much about not being able to install that extra phone jack. It was nice of you to put in two days of work, but it seems obvious now that there was a good reason that no phone jack was there to begin with. It just wasn't doable.
Sometimes life is like that...things just don't work out the way you want them to. You said that in your 11 or so years installing you've never not finished a job. Well, there's a first time for everything. Don't worry, I want to let you in on a little secret...after about your third hour here I decided that I really didn't want a phone jack there anyway. See no problem.
Also, please don't have anymore nightmares about not figuring out how to wire the house so the line will work. When you said that you were tossing and turning all night about the project I really felt for you. It's great that you take so much pride in your work! Very commendable, most people don't care about quality these days.
Thanks for all you hard work, but you have to let it go now. Nobody thinks any less of you. Go to your next job and give it your all.
Ma'am (women whose house you couldn't wire for a new phone jack)