That would have been accurate for a DNS outage ; but with my layman understanding of BGP, I would say the analogy would be something between "...but their phone line is broken" and "...but they disappeared from the phone book because they don't have a phone line any more" .
Actually, it probably is, especially if you dial the analogy back a couple decades before the "We're sorry that number has been disconnected" automated responses: Facebook's phone line went down and when you call the Operator even if you have the phone number, they can't connect you, but this is weird and you aren't the only one trying to call Facebook so now they are calling in other Operators to diagnose the problem because surely someone has heard from Facebook recently.
That analogy includes the snowball impact on the other websites and services as the Switchboard Operators get more over-utilized into puzzling out Facebook's problem than servicing calls for still working phone numbers.
