I don't think we need the tinfoil hat. This sort of thing happens sometimes. Like the time we forgot how to may part of our thermonuclear weapons and had to reverse engineer that [0].
The really interesting thing about that is one of the main things they had to reverse-engineer was an impurity in one of the ingredients that the original designers didn't even know they were depending on.
This was true of lots of things outside NASA. This was one of the problems that killed the UK attempt to modernise the Nimrod maritime patrol aircraft [0]. They wanted to fit new wings to the old planes, but only discovered after the contract had been signed that the different airframes had not been built identically, but were different interpretations of a common plan. Each of the nine planes was in effect a completely new refit challenge.
Interchangeable parts don’t.
Additionally the F-1 engines were redesigned using more modern techniques around 2012 with the F-1B [0].
The SLS went with the RS-25s for a number of reasons. While the F-1s provide high thrust they're not as efficient. The RS-25s can burn longer and with the SRBs providing massive amounts of thrust to get the stack off the ground the RS-25s can provide more delta-v to the upper stages. An F-1 reboot would have required a lot of extra work to add in modern computer controls which already exist in the RS-25. They have also flown in the past few decades and are well understood.
[0] https://arstechnica.com/science/2013/04/new-f-1b-rocket-engi...
Basically, someone created a F1 engine inspired design with modern manufacturing technology but ultimately it was never used.
In fact most 'stories' and 'news' is like that. The SLS is known to be in a congress sub committee hot potato game. So that there are different versions floating around of what happened and is happening is not surprising. Teasing out the 'truth' of what happened is not always easy. As many have interests in distorting it, or just remember wrong.
The whole "we can't make them anymore" meme has a tiny kernel of truth but it's been blown way out of proportion the more it's been repeated.
When the F-1 was manufactured a lot of the actual assembly of parts was done by hand. That meant Rocketdyne's engineers and machinists had a lot of tribal knowledge that was lightly or partially documented at best or not documented at worst. NASA and Rocketdyne maintained all of the designs and documentation and knew everyone involved in the engine manufacturing.
In the early 90s a lot of these Rocketdyne people were interviewed [0] and asked to review F-1 manufacturing techniques as part of the Space Exploration Initiative [1]. Restarting production of the F-1 would have been practical but more expensive than the alternate plan to go with an SSME derivative.
While the F-1 is an impressive engine it has downsides. It's enormous and heavy. The Saturn V's first stage (S-1C) was 10m in diameter while the Space Shuttle's external tank was 8.4m in diameter. The Shuttle's ET was going to be the core of the proposed SEI rocket (and SLS). With a 8.4m tank diameter it would be more difficult to mount more than two F-1s.
With only two engines it would be more dangerous of a vehicle for manned missions as a flame out in one engine could be disastrous. It would also make it more difficult to throttle the engines for different launch profiles. Moving to a larger core would have required all new manufacturing infrastructure, flight qualification, and unknown follow-on issues.
Tl;dr The F-1 was an awesome engine but not perfect or even desirable for all purposes and the "we can't build them" meme is stupid.
[0] https://www.thespacereview.com/article/3724/1
[1] https://en.m.wikipedia.org/wiki/Space_Exploration_Initiative
Also it is no longer known how to make the Saturn V rocket which flew to the moon - https://www.nytimes.com/1987/05/26/science/hunt-is-on-for-sc...