My mum had a slightly similar issue. She was traveling TK-SQ and TK lost her bags for about a week. TK's fault but when she landed she made the claim with SQ since they operated the last segment. When she got her bags it was clear that someone had gone through them and taken some stuff. Sent a letter to SQ who basically apologised but said the things taken we classified as valuables so they weren't ultimately responsible for under the contract of carriage.

She made a claim under her travel insurance instead (and needed that response from SQ to do so).

goodo