"Langdon" vs "him"

[Tom]

Hi

I read this sentence in Da Vinci Code, by Dan Brown.(Page:71)

1- Langdon knew Sauniere spoke impeccable English, and yet the reason he had chosen English as the language in which to write his final words escaped Langdon. He shrugged.

Why does the writer say escaped Langdon? Why not escaped him?

Thanks in advance

Ever yours

Tom

[Yankee]

Hi Tom

I'll take a wild guess about what Dan Brown might have been thinking there: Maybe he thought otherwise it wouldn't have been 100% clear who "him" was.

Amy

PS
Langdon and Sauniere both appear at the beginning of the sentence. Then the sentence mentions "he" and "his".
Who is "he"? Who does "his" refer to? Langdon or Sauniere?