Resolved: Weird "insufficient material" error

I'm not sure how the folks over here do their homework, but last I checked this is not a game with insufficient material...

http://www.chess.com/livechess/game?id=334824164

... this game ended at precisely the moment when my opponent's clock struck 0:00. (S)He was having connection issues, if that might be the cause of the problem (which it really shouldn't-- these calculations should be done on chess.com servers).

You had unsufficient material but in reality you should have deserved a loss.

If your opponent runs out of time, you can only claim the victory if you have sufficient mating material (more than king alone or K+B or K+N). Otherwise the game is a draw.

"deserved" -- hardly. I won the game on time. But I'm not sour about it or anything, I'm just reporting a bug and a bit curious as how such a thing happens.

edit: I suppose bwolf has answered my question.

Because if you win on time but you can't mate the other player. It's a draw by insufficent material.