oh speaking of leaving things!!
I ran a world from scratch server (no TP, no PC) for a while and after weeks of mining and crafting I FINALLY crafted a jetpack. I was so excited because other players had forged ahead and were already flying around. Then I came down to earth to save fuel but when I switched into a jacket from my jetpack, my inventory somehow filled up. I don’t recall how exactly because I didn’t even notice that in the switch, my jetpack dropped on the ground as I started tapping towards home. Only later did I realize it wasn’t in my inventory and had despawned!! d’OH!! I never crafted another jetpack on that world again.