After Beating the ender dragon and closing of the portal, I gained possesion of the Dragon Egg. I opened up the portal again (freed one block) and jumped in the portal.
The end screen came up. I skipped it using the Escape key.
I spawned back in my world with my entire Inventory EMPTY.
Egg gone, diamond pickaxe gone, armor gone, arrows gone, enchanted bow gone, ... Entire Inventory Empty.
I suppose this is a bug and not intentional ...