Bit odd isnt it. Customer unhappy about bill, and they tell them not to bother to pay it and go elsewhere. Not many businesses can afford to do this.
I would have thought that at the very least they should have contacted the manufacturer of the airframe and or oilcooler.
Obviously if you are concerned about the safety of a certain operation you can always contact the CAA and raise your concerns. They will no doubt be keen to hear from you and point you in the right direction.
Apart from not being particularly good practice to chuck a part away which needs replacing, it is also not theirs to do so; after all it is your property.
By the looks of things they may well have done you a favour.
FD