I talked to Toyota's main customer satisfaction rep this morning, and she is referring this to the Prius Green Team, who is assigned to look at issues with the car. I expect to hear from them tomorrow.
Meanwhile, my insurance adjuster came out later, and they will cover their estimated cost, although not the $90 I already paid the first Toyota dealer for diagnostics. Yes. They showed me a pinhole but I don't have superman vision so I couldn't see it really. Anyway, their offer was a little lower than the dealer's estimate, but it's up to the dealer to argue with the insurance adjuster if they want to.
Fortunately, the major work is covered by comprehensive (0 deductible). But I'd rather have it come from Toyota's warranty to be sure.
The Prius is now sitting at the shop waiting for the part to arrive.