When you're in the middle of a book promotion campaign, every interview opportunity is precious. Make sure to capture the details of every book promotion interview you have planned, and then have a backup of that information in another place, and then -- for real security -- back up that information again, in some other way.
The book promotion interview will probably go on, as planned. The interviewer probably has your phone number, and he or she will probably call at the appointed time, on the agreed-upon date. But you know what? Sometimes, not so much. That's why you have to take careful note of the name of the interview, and how you can contact him/her in the event that you need to. When you're scheduling the interview, or your book publicist is scheduling the interview, ask for a backup line (explain that you'll be using it for "Plan B," just in case there's a mixup the day of the interview). Then write down that information so you'll have a hard copy of it. Compose an email with that information, and send it to yourself. Type the information into the calendar section of your email client, and into any online calendars you might use. Write it down in your appointment book....
You get the picture. Make sure to memorialize the details of the interview, and then make sure you have as many copies of that information as you'll need to ensure that, if you should need it, you'll have it.
And don't expect your book publicist to act as your only repository of this information. Book publcists are human. We do our best to hold onto information, but our computers crash. We misplace things. We try not to, but it happens. And even a theoretically perfect book publicist has to heed the call of nature (or take the calls of other clients) sometimes.
Therefore, when you get the information about the book promotion opportunity, capture it, and guard it carefully. Don't count on somebody else, however well intentioned, to do it for you. It's your book promotion campaign, and you can keep it on course by being the best data keeper imaginable.