Uh...
1. Log in.
2. Find a backpack or a tent loaded with stuff.
3. Hit tab. Note that it is either empty, or haphazardly loaded with a few things in scattered positions.
4. Drop something inside (or pull something out).
5. See everything magically appear.
Screenshots here:
Before Inventory appears
http://steamcommunity.com/sharedfiles/filedetails/?id=355036545
After Inventory appears
http://steamcommunity.com/sharedfiles/filedetails/?id=355036573