I was Hoping when i built my house in game it would stay (like normal)

When i relog into my world there are no signs of my house and if i cut down a tree in my last play through the tree had returned to it's normal location

How it was triggerd was..
1) I log into my minecraft like normal and create a new world
2) The Menu flashes up again (Main minecraft Menu) for a split of a second
3) I build somthing (eg. A house)
4)I log off for a bit knowing i have pressed "Save and Quit"
5) I return to the world and all i done has be replaced by it's old block.