Hi Ben,
(Things seem to work better in the Moodle 2.0 TinyMCE editor: I was able to navigate away from this message and then come back to using my browser's Back and Forewards button and what I'd written was still there.)
Otherwise, for Moodle 1.9 I'd suggest using Firefox and installing Lazarus Form recovery and you'll never loose another text typed in Firefox.
Cheers,
Glenys