Single game
its not a bug, you can leave by porting back to heart of the mists.
The GW2 hot join servers are modeled after FPS servers: persistent games, joinable independent of game progress, that cycle through maps regardless of each player’s intention to keep playing.
I’m really happy with the current system, very little downtime at all. I can get right into a game, and even after it ends I’m not frozen stiff staring at the scoreboard. Works out great for maximizing game-time when you don’t have much to spare!