That's where you build your argument that they acted inappropriately and did not disclose prices (did they?). The next question is are you on a State plan or a corporate EIRSA plan? If State they you can file a complaint with the California department of insurance. If you have a corporate plan, which is likely self funded, then I would ask your HR to talk to your insurance rep. You might find things get retroactively covered at that point. Or you can talk to the news. They love to report on these things.
Stanford has pattern of inflated charges. Hearing tests in audiology for example are ridiculously overpriced without insurance and they don't pre-authorize. And most insurers don't cover hearing tests anyway. Stanford could fix this by not being greedy.