Hitchens didn’t really address Buddhism in any meaningful way. He made a quip once about the Buddhist saying this glass of scotch isn’t really there and Hitchens’ response was something about how he rejected that take because he enjoyed the scotch.

He seemed to dismiss it because it was a religion rather than address any of its positions in a substantial way. Probably because he couldn’t give as forceful or witty a counter argument to it as he could Christianity.

In God is Not Great, Hitchens unequivocally laid into buddhism, though obviously it wasn't the focus of that book, or, as you intimate, much of his work. But within, he attributes imperialism through to kamikaze indoctrination to buddhists / buddhist dogma.

I suspect the absence of (m)any proximal adherents willing to publicly debate him on the topic is why we don't have the same wealth of quips and ripostes from him around this pseudo-religion as compared, say, christianity.