you should have 16 disks.
your deal is with the shopowner. it is his responsibility to deliver you a proper product.
I always thought it (and still think the buck should stop with the shop if the publisher doesn’t play ball) comes down to the shop you purchased it from but more often than not after being passed to the publishing company the matter is resolved by them posting you the required parts. Out of say the 10 times I’ve had problems with game parts 9 of those times have been solved by the publishing house.
I think it’s more a case of the shop not actually having the parts to give you. I’m sure they could play middle man and request them from the publisher and then post them on to you but that wouldn’t be the cheapest and most efficient way.
Contact both I’m sure there is a good chance the shop owner will pass you on to the publisher and they will be happy to sort you out, the publishers normally are. If they don’t then I’d head back to the shop because I feel it is their responsibility. I’m sure both don’t want a fuss kicking up over a few pence worth of wooden discs.