Turkish Airlines Flight Delay and Lost Luggage Issue

There is so much to write, but due to fear, the complaint details are limited, and I can write only a little. My son, who had a ticket for Thursday at 13:05 to go to his school, was kept waiting at the airport for 16 hours and is being sent today, Sunday. Despite confirming his baggage before boarding the plane, he found out that his luggage was missing when he landed in Cyprus. This child is a student with no one there, and he has only one piece of underwear and no other clothes. We lost everything in the suitcases, and after waiting 16 hours at the airport and being denied boarding twice, we finally managed to board the third time, paying an extra ₺2,000 for the excess luggage. I am very curious about the answer to why the luggage, which was confirmed as loaded when boarding in Istanbul, is now missing.