Besides the scroll bar for the capsule, you should also have a scroll bar for the entire screen. This happens to me sometimes but all I do is drag the screens scroll bar down and I can move the capsule back into position.
If that doesn't solve it for you, keep in mind that the capsule has auto save every minute or so. So you may not actually have lost your work if you close the browser and go back in. Although try the scroll bar first.
One last thing, it's not a good idea to type your new work directly into a text capsule anyway. I do my creative work in MS Word where I can run a spell check and grammar check before uploading it.