Concert Absence

I'd been working towards a concert performance with a 15-yr-old girl.  For about a month, our focus had been the upcoming performance.  Then, with no explanation, she just didn't show.  In the lesson after, I asked her about it.

Me: What happened to you last week?  With the concert?
Girl: I'm so sorry!  I just ... forgot!  I walked home, and then... went... oh yeah...