You were lucky you had a Chev 4 blade fan and not a GMC 5 blade fan. That used to be a rather common sight. That is why it was common practice to push the tips of the fan forward at oil changes. Belts were so bad in those days too that they needed checking every time oil was changed also. The broken blades don't seem to want to go forward toward the radiator core, but I have seen them come up through the hood. 50 years ago, we considered a fan much more dangerous than multi-piece wheels.