No harm in asking the dealer. As mentioned, I've done it more than once. Nice and friendly over the phone, obviously not wanting names, personal information etc etc. Not too familiar with the 450h but at 4 years old there can't be many "extras" other than brake fluid change? If the car was older, I'd got the stamps but no invoices and couldn't get details from a dealer I'd assume none of the big items had been done.