Hi Bita,
Welcome to the Emirates forum here on FlyerTalk, wish it were under better circumstances.
From the available data on flightaware and flightradar, it appears there are two Emirates A380s at SFO at this moment - my guess is one has a maintenance issue that still needs to be resolved. Have you received information on how your parents flights are to be rebooked? There are other connection opportunities through LAX, Seattle, New York JFK and other Emirates gateways that you could ask to be rebooked on.
I'd give the call center another call and simultaneously contact @
EmiratesSupport on Twitter with your questions (A direct message may be required to give their reservation locator ID). If you are truly not satisfied with the answer, I would show up at SFO and talk to the station supervisor (he wears a brown chocolate suit coat).