Quasi Moons and Planet 9

So, I was following up on a piece  of astronomical news by Bruce Cordell on his blog about a new designation of asteroids. The original article can explain it better than I could: 

 https://brucecordell.blogspot.com/2024/04/the-moons-of-earth.html 

https://www.scientificamerican.com/article/earth-has-more-than-one-moon/

What particularly caught my eye is the piece about Planet X (here called Planet Nine) and the 

long and fruitless effort to locate some evidence that it exists. Instead this new approach is collecting evidence to prove places it's not, planning to solve the matter by process of elimination.

https://www.scientificamerican.com/article/where-is-planet-nine-its-hiding-places-are-running-out/

--John R.

The final intriguing bit for me is that observation that they might not find evidence it exists because it might no longer exist, in case they'd be looking for traces it left behind. 

Anyway, an interesting piece for those who like to put on their astronomer hat once in a while.