This has happended to me 3 times on Windows 10 bedrock, and my daughter once on iPad playing in the same shared game (the game is hosted by the Windows 10 PC). The games loads and the player is placed at a significant height above the original world spawn point. The falls kills the player, and the player is respawned at the last spawn point (although this seems to be a bit buggy too, as I end up on the roof of my shack, rather than inside next to my bed). I've been fortunate in that my saved spawn point is not too far from the game origin point, so I am able to travel back and collect my dropped stuff before it disappears (what is the timeout on this, BTW?) But it is tremendously inconvenient. I have taken to placing all my inventory in a chest next to my bed before saving and quiting the game. Obviously I also lose all my XP points, which is quite a PITA.
Forgot to says that this has only started with the 1.8 update.