I'm sure we've all seen a kitteh, absolutely immobile, watching, with intense interest, the hole into which a mouse or a beetle had fled . . . Nothing will distract that kitteh from its current task.
So after going through many pages of the list of
sheddyian's posts (in reverse chronological order), I can declare that I've found it!
To what do I refer? Just one particular
forum thread that was made back in 2013. (September 14, 2013, at 21:43:02, to be approximately accurate.)