Here is a list of pretty much anything that could have resulted in coolant in the oil pan:
Head Gasket
FO8 gaskets
Cracked block (including front and rear stud hole cracks)
Cracked head
Head core plug
Cracked cylinder sleeve
If you reduce to only those items that could totally empty your radiator into the oil pan, I would mainly list:
FO8
Cracked block
Cracked sleeve