I think it highly unlikely that a Lexus Dealer or any decent garage would need to cause damage to a clients car to gain additional work.
If it is a decent business it should be earning sufficient money to pay for it's overheads and make a profit, without stooping to dishonest tactics. Additionally, the risk of discovery (ie losing the franchise) is far too high to consider trying to make a couple of hundred Pounds extra.
I guess there is a possibility of a rogue Technician and/or Service Receptionist looking to boost their bonus by dishonest means? I don't know how Lexus Dealers operate a bonus system (if any), so this was only a thought. Chris Shipley may be able to help.
I very much hope you mistaken and are just a victim of misfortune :)