What does it mean when there's an empty chat box on Facebook? (10 pts)?

[jumpp&then` f a l l ... x]

I logged in to my computer and my friend's chat window popped up at the bottom, but it was empty. It said "Today" and then that she was offline, but it didn't say anything else. I had gone on Facebook on my phone and clicked on her chat name, like I was going to say something, but I never did. Is that just what it is, but transferred over to the computer?

I've always wondered this.
Thank you!