It would have been at the very moment that he turned to speak to Zahavi that she'd run away. Of course. At this moment, however, Izzy wouldn't have expected it. He'd turn back to Zahavi and say, "I never meant to be rude to you, sir. My apologies."
The second he glanced back was the second that the vampire was gone and the serving girl was going off somewhere, clearly unharmed. Suddenly, it didn't matter so much what kind of problems Zahavi had with him, Izzy had been stupid enough to lose sight of her and now...God only knew what she could have been doing. In an instant he went completely white and his mouth hung open a little, but he tried to control himself.
Standing up, he said, "It has been an honor and a pleasure to talk to you, Mr. Zahavi, but I am afraid that I must leave you to your," he couldn't think of words right now, "I hope the night treats you well, sir!" And with that he was off like a shot into the ballroom, where it became very clear that he hadn't the slightest idea where to go.