I died in my hardcore world and the screen that said "you can't respawn" appeared, but when I clicked delete world, I came back and the world was still there. This problem persisted for a while until the 5th delete finally seemed to get rid of it. The images below are of how it kept looping. I did this again and recreated the problem by spawning a world (hardcore) went into the ocean and drowned. I deleted the world and it just came back.