sometimes I'll go back and there's nothing there.
Another solution is to retrieve what's lost by hitting the browser's "forward" button.
The advantage is that you don't have to do it every time (only when you suffer a wipe-out); but the disadvantage is that you'll get, and have to manually correct, whatever changes the spell-check or preview made to your text. Seems to me faldage's method is better, unless you only have this problem once in a great while.