I was playing survival mode and was lost so I was thinking about switching to creative mode. So I quit to title went into my world options and clicked on creative mode. Then I read that I would not get any achievement if I switched back to survival mode. So I click back on to survival mode. Note I never entered the world in creative mode. When I went back to play, everything that I had in my inventory was gone.
Since I was lost, I ended up dying so I would respawn back at my house. Everything else was fine there, everything was still in my chest inventory.