He can't necessarily tell what she's doing by listening to her heartbeat or scenting her, but he can guess based on the way she's looking at him. He knows that look; he used to get it from Paige what seems like a lifetime ago. She doesn't know if he's making fun of her. So he waits until she seems sure that he isn't, because he isn't.

"Likewise, Felicity," he replies, shaking her hand and nodding a little. He can scent the mounting frustration behind him, but chooses to ignore it in favor of not being rude to the person looking him right in the face. It isn't lost on him that she's still sort of hanging onto his hand like she's forgotten to register the fact that the handshake is complete.

He looks behind himself with a pair of eyebrows lifted in question, challenging anyone behind him to say anything about the hold up. Then, he looks back at Felicity and gives a little facial shrug. "Yeah, you're probably right. Don't run off?" he asks before stepping up to get his welcome packet. She's right, after all. It's not cool to hold up the line just to chat with a pretty girl.