First of all, the timing belt is in no way related to the performance of the oil pump. True, the pump will not operate if the belt is not installed, but then again, the car won't run if the belt is not installed, eliminating the need for the oil pump to pump. Removing the timing belt may allow easier access to the pump, making the retrofit a smart thing to do if removing the belt as a preventative measure.
The chances are high that Honda had either a recall or bulletin about this defect, both of which were probably mailed to the original owner. Recalls have time limits so if you waited too long to bring the car to the dealer or if you were not the original owner to begin with, you are SOL. Recalls can't last forever and you did say your car is 6 years old.
Finally, your technician should have been aware of the condition and recommended the retrofit to you, however, he is not responsible for a part he neither removed from or added to your car. Seems to me that since you took the car to the tech and presumably told him you wanted the belt changed, you should have also told him to install the retrofit, since it seems you already knew about this "well known problem"
I had my timing belt replaced on my 2000 Honda Accord. A couple months later my engine started hemorrhaging oil because the "oil pump had walked out of the block". Previous models of Accords (1994-1997) had a retrofit clip recommended with the timing belt replacement because this was a known problem. I had to have the timing belt replaced again, this time I had them add the ($20) retrofit clip. Honda refuses to admit that this is a problem with my model, and would not pay for the second timing belt replacement. My purpose of this post is 1) to warn people to go ahead and add the retrofit part if replacing the timing belt, and 2) to see if anyone has an opinion as to why this may have happened that may not be Honda's problem (I did not have the timing belt replaced at a Honda dealer). After owning 2 Accords, I believe I'm done with them. I've been disappointed (in other ways as well) with the second car.

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