Professor Tsui could not be found anywhere last night - even by his colleagues. 'We've looked for him in his house and at his office, and we haven't located him,' said a Princeton University spokesman. 'He could be anywhere - he's very shy.' It was unclear whether the new Nobel laureate had gone underground to avoid publicity, or whether he simply had not been told he had won. His disappearance made things difficult for Princeton, which was trying to arrange a press conference for him.