MC Realms - Died - Shulker Box disappeared

Playing on Windows 10 Realms – I fell to my death. Within 30 seconds, my partner picked up my items to place them in a chest. All items were present except diamond pickaxe with Silk Touch and some other enchantments AND my shulker box with ALL of my valuables. This is not the first time I have died and something random (and very valuable) just disappears. I was nowhere near lava; there was no explosion; I searched high and low for my items. This is a show stopper because it was all of my valuables. Why do items just disappear? It really kills the Survival mode gameplay. Thank you for looking into this. I do not plan on playing again until this is fixed. I'd really like my items back.