Maybe. More likely to fail at full power. The fact that it didn;t suggests the failure was "progressive," crack grows steadily under a regular/modest load. Usually, failure under full power is more likely to be catastrophe becuase the aircraft is moving slow and has low altitude, and is also heavy wil as much fuel as needed for flight plan.
-- The ring was suppose to contain that blade. --
It almost certainly would have contained -A- single blade.
-- just read that the engine on a 737 use to have 24 blades. They now have 18. --
Varying numbers of blades depending on which section of the engine.
Going from 24 to 18 bypass fan blades is a reference to the bypass fan section, at the front.
More than you want to know about the CFM56. The engine on this aircraft is reported to be CFM56-7B