A similar situation happened to me. I had used my half-miles upgrade to get my gf a ticket from CM to LA. There were no Royal Silk seats left on the return LA to BKK to LA flight, so we got Premium Economy with the promise that if a seat became available in Royal Silk, we would get it. On our first morning in LA, I asked about the situation, and was told that the LA office took care of it already...without even a call. That day, I got email too.