I recall once that I put a caged queen in a hive without realizing that there was still a queencell in there. One of my many beekeeping mistakes. The virgin from the queencell left in a swarm - I guess she thought that the caged queen was the remaining 'queencell queen' and so had the all-clear for takeoff.
In your case, the virgin left knowing there was queen in the hive she couldn't kill.
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