I just installed FireChat on my Android phone. I joined a chat room, then left. Then I saw that it was still shown in a list of “Joined” rooms. The next time I opened the program, it practically forced me to join another room.
When I would go back to the main screen, I didn’t see any options to un-join one of the rooms that I no longer have any interest in.
I tried to swipe, and found that the name of the room would move a bit when I swiped, but nothing happened.
I closed and then re-opened the application and then all of a sudden I was able to swipe to the left, even when my finger wasn’t on the text name of the room. If I swiped far enough, it removed the room from my joined list. So keep in mind that it’s a little buggy, but you simply have to close and re-open the app, and then swipe to the left completely to unjoin the room.