You ran out of time. Are you saying you would have preferred a loss?
According to the rules, your opponent doesn't earn a win on time if it isn't possible to win on the board. It is impossible to mate with just a king, so your opponent didn't earn a win when your time ran out. That's why the draw is due to "insufficient material" - your opponent's material (lone king) was insufficient to checkmate you.

my move with king rook and pawn against bare king and game awarded berkshire100 a draw.