My opponent resigned when I thought I had lost

In the following game my opponent resigns in a capture race but I am not convinced that he had lost. During the game I was actually sure to be the one losing. I feel like even if black’s top group dies he can build up enough strength to kill my bottom right group and win. What do you think?

I added a variation to your game, black could have captured the central white stones. Black H11 was a big mistake.

I don’t see how white would die in the bottom right. White has 3 directions where to extend: center, right side (black has a weakness at Q8), and corner (living shape with R2).