How do I admit I lied?

Okay, so, on Friday, I wrote on my friend's wall on facebook (as a joke, not seriously) that I was in Taiwan for my dad's business trip and that I wouldn't come to school for the rest of the week (I even wrote "AHAHAHAA" as a hint that it was a joke). But then, my friend took it seriously and said stuff like "cool! how is it? how long are you going to be there?". I decided that she was joking around too, so I replied accordingly. Apprently, she thought i was serious. As a coincidence, I didn't go to school today, so she didn't see me in class and thought I was really in Taiwan cause I didn't come to school. Now, tomorrow, I'm going to school, and I'm gonna need an explanation for why I lied to her. If I told her it was planned to be a joke, she would ask why I didn't tell her when she started questioning me (how is it, how long are you staying, etc.). I don't really know what to do?