Did you run out of time?
If you run out of time and your opponent cannot checkmate you by any possible sequence of legal moves (i.e with a lone king) the game is drawn (in which case you got lucky).
Otherwise, it is a bug.
If you need help, please contact our Help and Support team.
In the last game I was playing on live tonight I got a "game drawn: insufficient material" when I was up a rook, a queen, and 4 pawns against a lone king. Does anyone know if this is a new bug for live chess?