Any vehicle owned by Toyota should have service history stamps.
My IS300h was originally owned by Toyota press and traveled more than 10k miles in their year of ownership - Lexus GB serviced and stamped the service book mid-year.
My GS was originally owned by Toyota press and hadn't traveled 10k miles in their year of ownership and so didn't need a service. When press vehicles go to the auction house that Toyota/Lexus use to sell on all their vehicles to Lexus dealers, that company services them at 12 months and stamp the service book.
If a Lexus dealership owns a vehicle, either as demonstrator, loan, or pre-registered showroom, they would carry out services themselves and stamp the book with their stamp.
Therefore there shouldn't be a case for services missing.