I had one a while back where the previous owner had used undersized shear bolts (1/4" vs 5/16"). When they sheared it off, it bent the end of the bolt and left a stub that was next to impossible to line up to get out.
I ended up getting one side aligned with the hole in the auger rake and tapped at it with an undersized punch and hammer till it started coming out. The rake actually rotated a little as it worked out.
Only other basic option is to pull the augers out of the housing then pull the rake off so you can get at the broken off pin.
Doesn't sound like fun, good luck.