I was playing against hookahey in the monster hunt league. At one point,he lost connection but he managed to come back before timing out for inactivity. A few second after playing, the game inactivity timed him out. I am quite sure there was several minutes to both our timers so it was not a regular timeout.
If I was to theorize: So if it was monster hunt... I'm assuming it was probably your turn, you moved, his maze of the mind triggered (time out counter starts for him) then he disconnects. He returns, chooses the location for your character. (time out counter continues to run because he hasn't played a card?) Now it's his turn and before he can play a card the timeout counter reaches zero? Would that do it @Flaxative?
Just wanted to report the same bug that happened in my ranked game with tiwx. I got disconnected, returned to the game, played 1 or 2 cards and then lost due to inactivity timeout. So this can't be explained like the previous case, it was definitely a bug.