What I think he's saying is that his chat box disappeared, and he can't pull it back up.
F10?
F10 is the same as pushing the button.
I think I know how to fix it.
If you only see the box, where you type in your messages, click in the middle of that, you should see a hand you can drag up.
So click in the middle or somewhere where you can see the finger pop up, and drag it up, that should work.
Sometimes you just pulled it down too far.