However, a few minutes later, and before white's clock had actually reached 00.00, the white player did return to the room for a few moments and then left again without actually coming back to the board, with the opponent again having to wait until black's time had expired.
The questions I ask are 'when does a game actually end ?' and 'could the white player have been trying to use some ''sharp practice'' to try and win the game?'
By not shaking hands; not resigning; not stopping the clock and not informing the arbiter; is white still technically playing the game even though the player has informed his opponent he does not wish to continue ? If so, would the opponent still have to sit there for the remaining time if white had, for example, an hour left on his clock or even decided at the start of the game to make one move and then walk away ?
It seemed very perculiar that white then returned to the room just before his time expired - could that have been in the hope that black had maybe reset the board and white would claim a win by ''illegal move'' ? (On this occasion, black had the sense not to touch anything until time ran out - and then offered a handshake across the board to his 'invisible' opponent !!!

I post this not only to hear comments and rulings on the incident but to warn others that not everyone observes the etiquette of the game.