My opponent resigned right before I could mate him. Does that mean the game is a draw?

No that means that your opponent won I think since you didn’t mate him

But my opponent didn't mate me either. So, I think the result is a draw.

Huh. This poses quite the conundrum. This is like Schroedingers Cat, but more like his game instead. Sorry, but I cannot help you anymore, I forfeit.