VERY SORRY to hear that BUT I don't think it has anything to do with the function of THIS forum, as I've had the same thing happen dozens of times on this (my own forum) and many others 'SOMETIMES' but not always.
I don't know the technicalities of how my forum works (I have a good customer/friend who deals with that) but I'm quite sure there isn't a 2 hour forced logout.
I'm told that late versions of Explorer can cause this kind of problem (which I've been using) and it certainly has caused me a number of other problems as well, one of which seems to have just recently self corrected after a year of mayhem.
As a consequence of all these such problems and wasted time, I now try to remember to either type my reply in Word before pasting it on a forum (therefore having it auto saved) or I copy the text from the forum response box BEFORE I press the submit button.
These practices have saved my HOURS of typing and allowed me to remain calm, because nothing makes me more angry than having to repeat lost work, so I know exactly how you feel. Whenever I get caught but such a problem, I have to leave it a day or two before repeating the work, because it annoys me so much I can't bring myself to do it straight away.
I hope you'll use my methods of safeguard against lost work in future and that they will save you the aggravation they've saved me.