The so long thong song

 Lost in the annals of time,

Twas a tale of of a twin unentwined

On a merry-go-round dropped?

At a Mount Perry pit stop

My thong and her pair 

Split - life being unkind.

To a group Perry bound I lament-ed

The divorce left me hopping quite mad

For this "three pairs for ten"

The least worst of a neat half dozen

Slivered art between feet and and the pad.

For years long the lone thong 

Formed an alter - strong in the hope that she - the other, the lost - would walk right back in to our lives. 

Hope disintegrates to despair.

Unable to bear the pain of the lost possibility any longer 

One Tuesday evening I allowed her to be taken away in a rare Marie Kondo moment - was I wrong?

Christmas last my eldest 'Salina cleaned the inside of my car.

Dusted the dash,
Flossed the furniture,
Defragged the detritus tween the 

Here I have to interrupt myself - I was getting a bit d- d- d- and I thought that I would try my ham French on AI and see what we could do. I was trying to convey the concept of car seats using attempted phrasing of "derriere" and the places where one may put theirs, and I thought "throne" and put an extra d- in there to continue with alliteration and to an Aussie chick like me, that would be funny.

The French AI did not think that I was funny, and suggested that I not use the Anglo throne, perhaps I meant "troner" and so I thought " well it does sound more French-y, try that" and the dumb French AI dude said that traditionally the French did not associate the derriere with the "troner" and, well, you see what's going on.

Based on the search results, "trone derrier" (or likely trône derrière in French) refers to a few different contexts, primarily a phrase describing something sitting in a place of honor, or a specific design brand:

Trôner derrière (to sit/reign behind): Used to describe something prominently placed, such as a, "La patronne du magasin trône derrière la caisse" (The owner sits/reigns behind the cash register), or a large sculpture sitting behind a bar.

Trone (Parisian Design Brand): A brand specializing in modern, colorful, and unique ceramic toilets and bathroom fixtures.

"Sprout a craqué son slip" (TV Series): A series where a boy's best friend is his own butt (derrière), which sometimes rebels. 

If you were referring to a specific image or phrase in a context not listed here, please provide more details.

Cracking on with the thong.

So I tidied the pile left behind 

'Mongst the boxes of things that you find

When you sift through your life 

Mother and daughter and wife

And up pops this one of a kind.

"I found her" I glee with delight

Then it dawns with true oversight 

That it's never to be

Lest the fates intervene 

And I binned her pronto without fight.

Now the moral, I am sorry to say 

For this lament of the one believed astray

Is missing complete 

Like beneath the back seat 

The thong was going Schrodinger's way.