Man, that sucks.

Unfortunately (particularly since the bolt is recessed in the hub) you will need to clear stuff from the front of it.

You might get away with just the radiator, if you're lucky.

Then try to:
* weld something to it, if you have a MIG welder and can get access (not sure if this will work).
* Bash a hex plug into the bolt (what's left of it) with a lump hammer and then undo it.

Good luck!