Huh?

The woman was not entirely unattractive. He seen better; he’d been out with much better, but it was surprise that hit him and prompted a chain of events over which he would have little control.

It was surprise and slight confusion he experienced as he was rather jolted out of thinking through what he was going to do following a tough meeting with a capricious client. It was surprise at the approach and confusion as to what he was hearing and what the young woman meant. He didn't think it had made sense, which he expressed with a quizzical “Huh?”