Items dissapear after I die

I was wandering around in the nether looking for a nether fortress and I suddenly got killed in one shot from out of nowhere and I lost all of my items upon death. I went to pick them up maybe 45 seconds after I died and they were gone. I tested this again in creative mode just to see how long it takes for them to disappear. As soon as I died my items flew around the area and disappeared a second after. now that I lost my diamond itemsI am wondering if I could get them back.