The title—What Happened to Goodbye—refers to a message that Mclean gets through her Ume.com account at the beginning of the novel. One of her friends from the last town she lived in is asking her why she just moved without saying goodbye first:
I scrolled down to my comment section, scanning the handful of new ones:
Girl we missed you already! The last board meeting sucked without you.
Beth, I heard from Misty you moved. Awful short notice, hope you are ok. Call me!
What happened to goodbye? (2.86-87)
This sets the stage for the entire book, and the problems that Mclean and her dad have with connecting to other people since the divorce. Mclean has a hard time getting close enough to people to even want to say goodbye to them, but in her time at Lakeview, we see her start to heal from the wounds of her parents' divorce. She begins making real friends—you know, the kind that she would say goodbye to if she had to leave again.