How often does this happen? Sounds really wasteful and expensive. But, without some sort of idea on the frequency of this, just what do you hope to accomplish? Is it against your procedures? ISO doesn’t say that you cannot buy cars, take the tires off, sell the tires (your product) and then scrap the cars. If this was an emergency, and was done to ensure that your customer got his order on time, and only done this once, it looks like poor planning and requisitioning. If it is done all the time, it would appear to be really poor planning.
I would probably start a little more research before writing it up if it happened here. If and when you do write it up, the evidence you find will be useful to the assignee in completing his investigation. Otherwise, if this is as deep as you go (I saw that you canabalized an assembly to ship an order) then, I think you need to just go to the department and orally report what you saw and let them handle it.
I guess what I am saying is at this point it is difficult to say whether this is a nonconformance or only a waste of purchased product. I wouldn’t want this happening, but I guess I could possibly see that it could be the lesser of two evils if the alternative was to lose a customer due to inability to provide their order to them.