You Need a diamond in your inventory.. Try do it on flat land... may not work on snapshot
You NEED AN ENDER PEARL

Step 1: make sure your heart (health) is below 2
step 2: throw your enderpearl directly above you
step 3: log off quickly ( i mean quickly )
step 4: wait about 20 seconds then log back on
step 5: collect scattered items

READ: this is how it works basically you can not die whilst your offline so when the enderpearl hits the ground lets say an invisible copy of you hits the floor and his/her items spread (not too far) so it dupes your items but you may not be able to find some of the items (you will not lose any items except for 1 ender pearl when you chuck it)