How did I get logged out in the middle of writing an EXTREMELY LONG intricately detailed and technical PM? I didn't click anything except the 'preview' button, I didn't even have any other tabs open.
This happens to me also from time to time.
I have the subscription page bookmarked, but from time to time I have to log in again…
But that this happens in the middle of writing is bad luck.
It was a reply to a post with links, pictures etc.
I did it over a second time, made sure I did even a better job so I could feel good about the extra effort.
When writing a long post or PM it’s not a bad idea to occasionally select the entire thing and CTRL-C to copy it to the clipboard. That way if you accidentally get disconnected you can CTRL-P to paste your work back in.
On my OPs I copy every so often to notepad and keep a history of each save.
I used to try to remember to always copy a long reply but you have to do it each time because murphy’s law loves to torment humans. That said, get Lazarus, it saves everything you type and will quickly repopulate your reply in a few clicks
There was a thread about this a while back, look it up, i also mentioned Lazarus there so that should make it easier to find.
This is the only forum/site I can think of that completely dumps any entered text on using the 'back' button, even with the same browser settings. It's bitten me more than once (especially in PMs, since on the PM pages you don't get the 'are you sure you want to leave this page?' prompt like in the regular threads). Accidentally bump the mouse button with your arm while typing and BAM! Everything's gone.
The site I’m sure sets an expiration date on the login cookie. Many sites do this. When it hits 30 days (to the second) or whatever the value it is, the cookie expires.
ooh i was looking to read those long technical stuffs… lol 
A few other things that could cause similar symptoms:
- Some browser plugin or third party tool is manipulating your cookies
- You expressly told the browser to clear the cookies/browsing history
- The browser’s list of cookies became corrupted and the cookie monster ate your login cookie
I did it while you weren’t looking.
Sorry about your troubles. :( Yes, the login session cookie does expire automatically.
However, I did confirm that with Firefox I can post, and then hit the back button and retrieve the contents of my post. I also tried disconnecting my network, hitting post, and then using the back button, and the post contents are still there.
I just recovered a reply when i clicked on post reply on another forum and it took me away from quick reply, it was only one sentence but it was only two clicks to recover
Had this happen too and always to a long post with multiple links, pick, etc. Back button works sometimes but not always.
Sorry, I guess my newest flooder put a bit too much of a load on the power grid and caused the servers to reboot while you where typing 
chrome caches a copy of the complete webpage, so as long as you go straight back, you are usually good.
I had this problem with paypal while dealing with a dispute. Now I always type it up, copy and paste it in a new email and it has spell check too and then post it. If its something about a light I might save the email in the drafts section in case I need to post it again or send it to someone. Its easier than trying to find it where I posted it. If I had to re-type it I would forget something and I type S L O W. Life is too short.
I’ve run into it elsewhere as well. Like other suggested, I sometimes copy to the clipboard or notepad - or just compose the post in notepad. Really that’s not something I do here, just something I’ve done on other forums where the problem is much more prominent.
a quick and dirty way to make a copy is to duplicate the tab using chrome. it won’t save the data, but you can always copy and paste.