Scaffold problem

I was standing on the new scaffold block to work on the ceiling of my base in my survival world. I logged out of the world because I wanted to check my creative world to review my ceiling plans. When I logged back into my survival world I was greeted with a screen stating that I had died. My character was in mid air above my original spawn point, my items scattered above a forest in the dark. I picked up what I could, which was practically everything but my Elytra. I pillared up and saw it in a neighboring tree. By the time I got to the tree it de-spawned before my eyes. My first Elytra that took me days to find. Ceiling plans on hold... back to the End.