Item despawning before 5 minute

So basically I had full netherite gear and tools and and elytra with all enchantment, and i want to find silent trim and swift sneak so I travel through ancient city 2000+ block from my base, I died one time from a warden, and when I came back all my item are there except the ender chest, I don't mind cause I can craft that after, then I die a second time of course on warden again, and when I came back some of my item are missing before 5 min, and suddenly I spawn warden again and died of course, and when I came back before 5 min!! All my items are GONE! I don't know if it's a feature or bug, but I'm so pissed rn, I search through online, if a warden can despawn item,it's said it might be a bug or feature, but I don't think it is a feature,and now I left empty handed, full netherite gear and tools elytra enchantment, loot i get from ancient city, gone FOREVER! Just like happen from my old world which is all my item despawn from water current, I hope i can get a clear answer and fix this cause I'm so PISSED RN, AND I HAD TO START FROM THE BEGINNING. Thank you