Cars can be stolen from any valet service, even from locations that seem very safe.
As reported by the San Jose Mercury News:
"Unit block of Miramontes Point Road, 5:15-5:20 p.m. Friday An attempt to steal a vehicle was made by a person in possession of an old valet receipt. When asked for a vehicle description, the person ran off."
Based upon this information, it appears the incident happened at the Ritz Carlton Half Moon Bay.
Notice that this is not a big city area, or even a small city. It's semi-isolated. Yet, some scumbag still decided this would be a good place to try to steal a car. (Where did he run off to?)
The valet parking service did a good job of verifying ownership by asking for the valet claim ticket. This is a vulnerability though with a lot of other valet services, because some valets give up cars without a proper claim ticket being produced. And sometimes people come out to ask for their car and it has already been given away.
I did some digging around... the valet service at the Half Moon Bay Ritz Carlton does not have a spotless track record:
From TripAdvisor: “Valet Parking Thefts”
From CreditSesame.com, section 6 on this page:
"One thief recounted how he and some friends spent more than a week at a luxury suite at the Ritz Carlton at California’s Half Moon Bay, and on his way out convinced the valet to bring round an expensive Lexus he had spotted earlier in the parking lot."
Ah ha... I can see why they have a strict regimen of asking for proper claim tickets now. They've been hit before!