found myself disconnected from tygem, but could not find the game / room / board I was playing. Because of the 5 min d/c lose rule, I lost the game.
To help others (or me) in the future, please give some advice on how to resume a game.
You should log into the same sub-server you were playing in order to resume the game. When you log into the same sub-server, you will be able to find a pop-up that the game you were playing is suspended, and asking you whether you want to go back to the game room to resume the game. (The server is not smart enough to direct you to sub-server you were playing)
Simply clicking the button 'Yes' will do what you want.
Note that I play Korean version, not the international one.