Exported an XML of the Project, loaded it into X-FX Handler, and Kaboom!
Look at this missing Hawaiki Effect! FASLE! That's right! But, but, hold on a second... That's fine and dandy, but WHERE CAN I FIND IT IN THE TIMELINE?
Ah! Ah! Here is the secret weapon: double click on the missing Effect and Kabaaahm!
It's enabled on CLIP0000180 - THAT I CAN SEARCH FOR IN THE INDEX.Three Clip0000180 in my Timeline indeed, and the third one wins the missing Effect prize.
(It was actually OFF!) Delete. Good riddance.
Thank you Andreas Kiel, Spherico.