How does a propeller "fall off"?

If they were able to make 16knots, it must not have been that big of a broken thingy-majigy.

The Norwegian Jewel has been moored in Oakland’s outer harbor for a week; rumor has it that it’s not moving for a while. Maybe enough time to fabricate a new prop but not sure if it could be fitted there.

Did Jewel actually sustain a casualty or just looking for a parking space?

The Norwegian Jewel is in Oakland for parking along with two other cruise ships (Seven Seas Mariner, Regatta). Port of Oakland traffic has fallen enough to accommodate berthing for at least a month or two. This doesn’t mean it isn’t down a prop.

This is from the link in the OP - it’s written by a passenger.

The propeller, hurled up by the rotation of the engine shaft hit, the ship’s hull. Fortunately, it did not slice through the metal and make a big jagged hole before sinking to the bottom.

Much more likely a blade or a piece of a blade. How would the rotation of the shaft cause the whole propeller to be “hurled up by the rotation” ?