Sorry bagpuss but it's gone I'm afraid.
The only tip I can offer you and other forum members, is that when you are composing long replies - before you post / submit / send - select the entire message (CTRL + A / right-click > select all) and then copy it (CTRL + C / right-click > copy).
That way if something goes wrong you can paste it back (CTRL + V / right-click > paste).
Cheers,
Shaun