Failed as a manager
First of all, he failed to notice which customer he was talking to, or didn't care.
Second, as a manager, you do not immediately defend anything. You get the customer's side of the story, then you tell said customer you'll call back. Then you go get the recording of the call and listen to it with the helldrone.
THAT is when you can decide to defend the guy, or, as it should have been in this case, drag him over the grill, then call the customer back and be all sweet and helpful and replace the doggone drive.
He deserved to lose that contract.