That parking lot drawing description does sound familiar. When you mentioned twelve parts, the first thing that came to mind was BBC's Twelve Years of Christmas (http://bigboobedcanuck.livejournal.com/188686.html). I didn't take time to look at all the chapters before I responded, but it's been awhile since I reread it and it's a wonderful fic, so I'm going to reread it, and if you haven't read it before, do read it. Even if it's not the one you're looking for!