Did he leave me?

I've been getting to know a guy for a few months. We would talk for hours each day, and he recently bought a plane ticket to visit me (I have the confirmation number and everything.). We were CLOSE. Suddenly he disappeared in the middle of texting one night and hasn't said a word to me in a week! I've left messages asking if he's ok and saying that I'm worried, and NOTHING. But Facebook says he's seen them. I'm so confused. Why would sometime disappear like that?