My Shulker box is gone and i don't know why

So i spent over 2 real life days gathering resources for a wither skeleton farm, put most of it in a shulker box, then when i go to my inventory to grab the shulker box, its literally just gone. I SPENT A LONG TIME GETTING THAT STUFF AND IT JUST GROWS LEGS AND RUNS AWAY? LIKE REAAAALLLLYYYYYYYYYYYYY AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA DAMN ITTTTTTTTTTTTTTTTTT