Because he tried to save his mother, Sam is now trapped in the alternate universe with Lucifer. Needless to say that the Devil is anything but pleased and Sam is the first to fall victim to his anger and rage. After being literally beaten unconscious, Sam wakes up to find Lucifer gone.
Knowing he has to survive somehow until Dean finds a way to get him, Sam does what he knows best and tries just that. He does meet Lucifer again, but this time he is different. They team up, if only to not walk this wasteland alone, and soon find themselves trapped in a cabin to seek shelter from a terrible storm outside. With little else to do, they end up kind of talking, which isn't going all that well. Until Lucifer finds something they can kill a bit of time with: an old magazine.
What Sam spots in it is some kind of quiz that’s supposed to create love for someone else, but of course he doesn't believe a word of it. Still, they are alone, they have to do something until the storm is over, so it won't hurt, right? He's not going to fall in love with the Devil after all, so he has nothing to lose. It really can't get any worse than it already is.