I know this thread. I am not commenting who is right and who is wrong. My question remains:
* If already lost a part "before the bag was opened" could it be missing already during packaging by Tamiya?
It may be valid that the shop should be responsible to try to get the part back but the posts sounded like the shop was to be blamed for losing the part, which seems contradictory to the above.
P.S. I have no affiliation with the shop. Frankly, I don't even know where the shop is.