The reaction was a complete lack of reaction. Physically, Bruce let nothing show. He had experience at such things.
Mentally, it felt like someone had punched him in the stomach. Without the suit.
A lot fell into place, although admittedly he was still sideblinded. He knew Mia well enough to know she would not be coddled. Either way, he could deal with the rest later. Right now, only one question mattered.