Recently I was at a USCF tournament. Six moves into my first round game, the tournament director came to my board and had me stop my clock. It turned out that the person across from me had the wrong board - he was actually supposed to be at the same-numbered board in a lower section (which was playing in the same room.) And the opponent I was supposed to play had sat down at the board in the lower section.
The TD stated that he was nullifying those two games in progress, and that those clocks should be reset and those games restarted with the proper opponent.
Is this the proper action? Can a game in which multiple moves have been played be simply nullified? Also, since my opponent was not at the correct board at the start of the round, and I was, and I properly started the clock, should some time have elapsed from his clock when we restarted?