Inventory items and xp disappearing

I was playing and then switched to a different app. When I went back on, Minecraft seemed to take forever to load so I closed and then reopened it. When I eventually got on to the world I was playing on I was alarmed to see that all my xp, armour and items were gone.

(In the photo the 1 xp and the iron are from the iron I just picked up out of the furnace)