Since none of us were there and don't really know what happened, here's my take just for grins.
A cruise ship underway doesn't have lookouts posted like some WWII destroyer in a Victory at Sea film, with grim faced determined men continously scanning the horizon with high powered binoculars. There is usually one bridge officer on watch, who has to keep a look out, monitor the ship's systems, handle communications, and deal with everything from adjusting the stabilizers to keep the passengers from losing their lunches to making sure the pools are kept full for the kiddies to swim in.
The Captain doesn't sit in a tall swivel chair in the corner of the bridge all day scanning the sea lanes. He's efffectively the Chief Operating Officer of a huge floating corporation, and his days are filled with meetings with department heads, from engineering to hotel services to human resources.
The radar return on a small, probably fiberglass boat with an outboard is negligible at best. It would most likely be invisible on radar unless the seas were completely flat and the radar gain had been turned way up.
On a cruise ship, there are very sharp class distinctions. Hotel staff do not associate with ships officers, any more than an Army private can go hang out in the flag officer's lounge at the Pentagon. Attempts to do so are probably not responded to pleasantly.
The birdwatchers were in fact playing the part of lookouts, and spotted the vessel in distress. They probably grabbed the closest crew member they could find, who was most likely someone from the hotel staff - a beverage server, the gal handing out towels at the pool, etc. You can find them everywhere and quickly, while you could hunt in vain for hours to find an officer.
That person probably tried to find someone who could communicate with the bridge, because they were not allowed to. Giving them the benefit of the doubt, they probalby thought that had succeeded. Apparantly they didn't.
An article I read said the crew member told a member of the onboard sales staff. This would be someone who lived in both worlds. They could be approached by someone from hotel services, but would be able to connect at some level with the ship's command. They would still be pretty junior though, and couldn't just call up the Captain. This would be the equivalent of the deputy assistant parking lot manager trying to get into the CEO's office.
It's unfortunate. But I'm pretty sure we probably didn't have a case here of "whatever, I'm too busy" on the part of the Captain.
But who knows. Maybe he was trained on the Costa Concordia.
