Nope. Not a single way to get it back.
Here's a Pointer for the Future.
Copy your Entire Document. The whole thing, Before you hit "Start Discussion" Paste it in notes or something...
Then, If it goes AWAL, You've got a spare.
Altough It may seem Dumb that you loose it all, There's a reason for that.
After 20 Minutes of Being Idle, THe system assumes you forgot to Log out. As so, It logs out for you.
This tends to happen in the middle of Discussions.
Another thing you can do, but I wouldn't fully trust, Is open another window, and log into the forum, It renews your time. Then post the Discussion.
Life cannot be contained, it breaks walls, crashes through barriers sometimes painfully, but uh... Life uh, finds a way