Last night I logged out of game after I had a massive lag spike in Dion. It was late and as my character didn't move for several minutes I decided to shut down and go.
About 10 minutes later my boyfriend (who was on a comp behind me) ran through Dion on his SE and there was my character standing where the lag spike had been. He was able to buff me and as we are in the same clan checked if I was registered as on line. I was. 10 minutes later I was still there, a full 20 minutes after I had closed my computer down.
you most likely had a problem with your isp. When you get a bad lag spike like that and stay in game is because your computer is not able to keep sending packets of info to the l2 server, discon or otherwise.
I had the same problem a couple days ago. I checked my pop up blocker, then my firewall, and then figured out it was that funny little box that connects my computer to the cable based internet. I unplugged it for a few minutes, then robooted my computer. All is well again.