Mystery of missing baggage on flight QR 920 by World best airline

Early August I travelled from South Africa to Auckland on Qatar Airways, on arrival in Auckland my one very large suitcase was missing, now 18 days later Qatar Airways with all their sophisticated systems are unable to locate the suitcase It really amazing that with all the super sophisticated systems that they have an entire large suitcase can disappear and after 18 days no trace really makes you think !!!! Still waiting for the first reimbur*****t from Qatar Airways its taken 10 days so far and still waiting Amazing how slow they can be when payments have to be made ????