I had a group running, went down to get a pizza that was delivered and when I came back up my entire group was in the lobby. No corpses and not running GTFO. No tells but in say someone named Moonbear had said the letter v. Super odd was all. No Moonbear was on the /who all and nada on Magelo.
I had a similar thing happen to me once. Came back to find my grp in the guild lobby. Happen to be that I had used the corpse summoner in the guild lobby and apparently they were not rezzed or they didn't poof and I scrolled back through my chat log to find out someone said something about getting all the corpses rezzed up in the guild lobby. I had autoaccept rez on so apparently my group got rezzed to the guild lobby.