idioms - How had you known?

I caught this dialogue on TV:

A: Who was that guy you spoke at the parking lot with?

B: How'd you known?

The second sentence, as I understand, is a contraction of "How had you known?" It seems to me that Present Perfect should be used here—"How have you known?" because the situation is unfolding now.

I can see using "How'd you known?" in a dialogue like this: "– I didn't support him, because I knew he was a betrayer. – How'd you known?" But I can't justify using it in this dialogue: "– Bad news, the game was postponed. – How have you known?"

Answer

I am 99% certain that what you actually heard was:

How'd you know?

(Note know instead of known)

This is expanded to:

How did you know?

Which in the conversation carries the meaning of:

How did you find out that I spoke with someone in the parking lot?

Or something similar.

"How did you known" doesn't make sense in English, so I'm fairly certain it's not what was said, and I can't provide you with an explanation of its meaning.