United Airlines Failed to Resolve Lost Baggage Claim

After my flights TK 0201 and UA1303 on January 20, 2025, I realized that one of my suitcases was missing and contacted both United Airlines and Turkish Airlines. A baggage report was created at the airport under reference number LAS20401M, and I was informed that the missing bag would be delivered to my hotel. However, no delivery was made to the hotel, and I received no further updates. When there was still no progress, I was instructed during a phone call to 1-800-335-2247 to purchase essential items out of necessity. After returning to my country, United Airlines did not provide any response despite multiple attempts to contact them. In my conversations with Turkish Airlines, I was told that the responsibility lay with the last operating carrier and that Turkish Airlines could not be held responsible. However, I purchased my ticket through Turkish Airlines and was harmed by an airline operating under a code-share agreement with Turkish Airlines. The missing suitcase contained a Samsonite Hard Case Luxury XL suitcase, three pairs of jeans, ten T-shirts from various brands, one Hugo Boss jacket, two pairs of shoes, a Dior perfume, an electric toothbrush, underwear, one iPad, three sweaters, and a medication bag, with a total value exceeding 2,000 euro. At the request of Turkish Airlines, I uploaded all required receipts, invoices, and documents through the website, yet for approximately 11 months I have received no concrete response and my case has not been resolved. From a corporate and professional airline like Turkish Airlines, I find it unacceptable to be left without any response for such a long time and to see responsibility entirely avoided. I am requesting compensation for the value of the items in my lost baggage or, alternatively, the issuance of a free airline ticket, as well as a formal apology for the inconvenience and hardship I experienced.