I was in my world and went exploring a bit only to find a ton of items and xp on the floor. This is a single player world that sometimes my siblings play on. So i picked them up and looked like items my sister died with. My sister hasn't played in about a week and no one died for about 2 so im not sure how every item and experience is still there?
Have you been in that area recently? Items only despawn if loaded in for more than 5 minutes. If you're far away their clocks won't count down.