Game Drawn Due To Insufficient Material?

If you don't have enough material to checkmate your opponent, you will get a draw if your opponent runs out of time. If you had run out of time, he would have won as he could have delivered checkmate. The rule is such that when your opponent runs out of time you get the best possible result you could get with your remaining material. With a lone king that is a draw, if you had one pawn left you would have won (as you could promote it).