If you look at the picture, you can see the locating slot for the pin (bottom arrow) The only way that pin can get to the crack case is if it goes though the oil hole (top arrow) and then drops though there and out into the case. This woudl mean though that teh cases have a huuuge score in them and the bearing was so loose that the cases must be totaled.
The other option is someone has built it wrong and has put the locating pin for the bearing not in its slot but on the oil drain hole (top arrow) and its fallen out. If thats the cases you shoudl see damage aroudn that oil drain hole where the pin has hammered back and forth.
_________________
If I have to take the carbs off once more...