losing most items after death

First of all, I had put my character in my house before turning my phone off so i could get a drink.Then had I came back and it showed that i had  i had died. at first it was okay because i was next to  my bed and i could just get my things back. But, for some reason at least 3/4 of my inventory had disappeared when i collected it. I had lost my enchanted iron chest plate and my diamond pickaxe and my iron sword and a lot of building materials