This issue is already in the known issues.
It happens sometimes, when you log out on or right next to vehicles, and log back in.
Until there is a fix for it, all you can do is to teleport to another area on your map by command.
Open your console by pressing F1, go into debug mode by pressing 'dm' in the console and pressing enter, teleport to another part of your map by entering 'tp 0 0' and pressing enter.
This will display a lot of red text errors in the console, but should teleport you to the center of the map. If it doesn't, please try the command again.
If you lost the items you had, it may be easiest to just spawn them in from the creative menu.