That question, I can't answer. The only thing I can think of is that their calls were supposed to be diverted to an automated announcement, but that your number was programmed by mistake. Their good fortune and your opportunity to be of service!
You are right! Thank you. You know, it was as much of a relief for those in SF to be able to let their loved ones know they were O.K., and not to worry.
My point being -- I have no doubts that those in the afflicted areas are not just coping with the devastation, but probably worrying about those worrying about THEM!
I've lived in quake areas all my life; the 1987 quake was... bad. But folks around the country were seeing NON-STOP footage of the "damage" areas, in their worry and concern. There were areas of SF that were doing better than others. I'll bet the automated "call diverters/auto messages" are on triple time, due Katrina.