I'm sorry to hear that your session timed out and took your post with it, l'homme.
Are you on a public computer or one shared with people you don't trust? If so, you should click any button (e.g., Preview Post) now and then so your session doesn't time out. I find it useful to preview posts every paragraph or two anyway.
If you are a personal computer, there's a better solution. Check the "Remember Me?" checkbox when you log in, and you will no longer have this problem because your session won't time out.