air travel – Bookmarked flight not searchable but bookable. How?

First time posting here, apologies for potential mistakes in posting etiquette.

I had a weird situation regarding booking flights which I’ve never encountered before in my travel history.

I’ve a “tracked flight” in google flights from AMS to LAS, business for 1375Euro. See screenshot 1. I can still book this flight with AA, if I click on the link from the tracked flight in google (screenshot 2). The weird thing is, that this flight doesn’t show up anywhere else I search. Obviously, I found the flight initially through google flights.

It’s not visible on the AA search enginge, not with BA, not with Finnair, not in Google Flights, not in Matrix ITA…cant find the flight anywhere.
I did all searches from the same machine, same IP, same country, etc.

My questions:

  1. How is it possible that there are flights which are not announced but still bookable?
  2. How can I find more of these types of flights?

Screenshot 1:
Screenshot 1

Screenshot 2:
Screenshot 2