Hi good people

On Thursday I was due to fly from SIN to LHR on a V class ticket, I did check in online, but it became apparent later that day that it would not be possible to make the flight.
I contacted the company I work for so they could change the flight.
But my forgetful manager, did not inform the travel agent until 30mins before departure.time. Later the travel agent conatcted him to say the flight had been lost due to me being put down as a no show and they would have to rebook a new ticket. Now when I look in MMB I see that the original PNR is used for this "alleged" new booking. I though new booking would produce a new PNR number.
Or am i missing something here?