I'm going to throw out a guess, so someone correct me if I am wrong.
There is a time limit for replies, similiar to a online bank account, where if you are not doing anything, it times out. Unfortunately, after you press the back button, you lost the reply. A quick solution is to copy all the text next time, and if it happens, just go back and paste, that is the quickest solution I have found. Copying it takes a second, and covers my back.