I doubt you've ever seen me be this blunt.

Amazon, for me as a vendor, sucks!
12 months, around 600 emails, and screwed over big time, with lies at every turn.
Couldn't resolve, and even begged family that works direct with Bezos, even visits his house
to interfere.
There is a big mess behind the scenes.
Fortunately, is mostly limited to jewelry.

For the op, sounds like the vendor processed shipping, because a vendor is penalized for not doing so timely and didn't have the product on hand.
It's done all the time.

I'm sure you'll get it resolved, but hope you might not open a can of worms, as one customer can actually destroy the livelihood
of a company that feeds their family from this.

One reason for the BS excuse is if as a vendor, one goes before the all-nothing Amazon Gods of Judgement,
One has a chance of it passing through with a "warning", if the customer complains.
If they simply said, sorry, I screwed up, my fault, this admission gets a Negative "Strike" on your vendor account.
There are thousands of stories found on the net of honest Amazon Vendors kicked off, because of a couple of customer complaints,
sometimes erroneous.
One for me was a large Swarovski Tanzanite Crystal, using their International trademark description.
The piece was under $20, and the complaint was why it wasnt an $1800 gemstone.
I lost that one, yet today as then, Amazon themselves will use the same "wrong" words,

The complaints that go to behind the scenes, wont show on their rating.
While the overwhelming majority of vendors are fine, its more a matter of a "no mistakes, or complaints allowed".

As a consumer, I understand your issue as well as all other threads.
As a vendor, its hard to be perfect.
The $20 concession will make you feel good, but its also to encourage you not to express a negative feedback or complaint.

In lieu of vendor ratings, I am more than aware of boiler rooms in China, that coordinate purchases, behind the scenes refund,
and controlled positive feedback.

If this falls too low, they suspend the account for review. They will freeze your funds, and close out and transactions, including cancelling in mid process, leading to more complaints....."I ordered, it showed in stock, and Amazon cancelled my order, dont buy here"

Shoppers for the competition have happened. I found such "shopper" that over shopped, returned all and complained on all,
to be employed by my competitor. Couldnt get anyone at Amazon to tackle this issue.

The tipping point to my account being closed. 99% positive, large positive feedback

All the time, but mostly Chinese sellers.

I have been approached to do this by at least 100 Chinese factories, in my field.

Its not prevalent in most products on Amazon. I wouldnt worry unless its "too good to be true"

The factories that do this are generally very large, very smart, and mostly good.
They just get involved more, Like the $.99 piece with free shipping on Ebay.
(Sterling silver chains....

They do this to fast track sales, and it works.

Certainly Hotel, and food have their own share of generating positive reviews.....free advertising is how its seen.

I dont like it, but happy to share some of the behind the scenes crap, that industry became and I lost my passion for
what happened.

Appreciate letting me vent!

Sure beats the stories from my elders waiting 6 months plus for a hammer ordered from the sears catalog!!