I just spent 10 minutes writing a topic about a duplicate text bug I found in 2.5. I hit “preview” to make sure it was formatted correctly. The forum told me that there were “too few characters” in my post and deleted it all. I can’t even go back a page and recover it.
I give up 
Sorry about that! 
Maybe the session timed out or something, I’ve never seen it happen that way, usually you just get a warning that the session expired and it lets you try again, but it sounds to me more like the browser lost your text before it was sent, so it ended up sending nothing to the website, and displaying nothing in return, and since the text was lost, it wouldn’t be stored in the history either.
As one who puts a lot of text into forums on a daily basis, I gave up on trusting browsers for content entry, years ago. I type everything in a stable editor and then copy and paste when I’m done composing.