Same thing just happened. Except, a couple mins later, I had a 15mins timer at the top left, telling me I would automatically concede. After that 15mins, the timer actually started increasing from zero (currently at 8mins).
I also couldn't concede. Had to close the game and then when I came back it was like it vanished.
EDIT : Happened in the next game too, on my side this time. Seems to happen when a player uses an ETB effect of a creature on another creature. First game my opponent tried to copy a creature with a Mimic, on the second I tried to exploit my own creature.
Same thing just happened. Except, a couple mins later, I had a 15mins timer at the top left, telling me I would automatically concede. After that 15mins, the timer actually started increasing from zero (currently at 8mins).
I also couldn't concede. Had to close the game and then when I came back it was like it vanished.
EDIT : Happened in the next game too, on my side this time. Seems to happen when a player uses an ETB effect of a creature on another creature. First game my opponent tried to copy a creature with a Mimic, on the second I tried to exploit my own creature.