Not doing the 30,000 mile inspection will not void your warranty. Even if some thing broke that was directly related to the inspection, I do not see how they could possibly deny your warranty.
Even if the particular dealership you go to wanted to try and take advantage of the situation, how could they prove that you didn't take your car some where else to get your 30,000 mile check up? For example, I do all the oil changes and inspections on my car myself because every one else is too incompetent to do any work or service on my car. Just because the dealership doesn't have oil changes and inspections logged into their computer, that doesn't mean that the service wasn't done to my car.