Good one Donk!!!!!!
That is where I get fuzzy. Surely a singular existential statement like "earth exists under our feet" is fact. The question in my mind is if such a statement should be part of science because it is 1) falsifiable and 2) confirmed.
Who would doubt that the Earth exists under our feet?
I say it is a scientific fact, with a few slight semantic issues cleared up: It is true because "the Earth" is just what we call this planet, and there's no doubt we are
"on" a huge object of the type we call a planet, while the meaning of "under" is defined in terms of the planet itself. You could reduce it to the fact that planets exists and we are on one, or at least this one that we're on exists, according to how good your telescope data is...
Your question appears to be much related to trying to match things up with Popper's ideas and I think these are the things he kinda glossed over a bit. I don't worry too much, I just reason on these things myself and I'm also aware of his ideas.
Clearly singular statements can be part of science. A statement like "this thread will break" or "the moon is made of cheese" is falsifiable. We agree that they are not intended to be candidate laws or theories. Beyond that—calling them "scientific fact"—I'm just not sure.
In the case of "the moon is made of cheese", neither am I so 100% sure about calling it a scientific fact, but its negation definitely is.
Some people would look at a video of Big Foot and say that "Big Foot exists" is verified. I don't think that necessarily makes is part of science. If I were personally making a criteria I would say that the statement needs to be reproducible.
Why not make one?
Nobody granted Karl Raimund any special licence for it.
We must keep in mind though that reproducibility isn't always an available option. I don't think Big Foot exists, cuz I've never got into a tangle with him, but I don't say "I think he doen't exist." because I'm not sure there has been an exhaustive search that could rule it out. Do you have a link to videos that are reliable and convincing?
Now if Tom, Dick or Harry says he was on a lone hike and saw the critter through the trees and whipped out his cell phone to take a video, people will say it's a lark, rigged up with a friend of his staggering around in some beaten old furs. Suppose one day Dawkins says he saw BF while he was out with his camera crew, he shows us documentary quality videos in which he can even point out some interesting zoological features; how many people would scoff at him?
Reproducibility can't be too stark a criterion; there always will be grey area and pretty vast too, it even includes lab experiments when they require mammoth investment. I've only been to CERN, once, I wasn't even participating in any work it was just organized by my physics dep't for students who might choose any particle related courses. All the same I wrote my thesis on stuff based on ISR data which had been analysed by Amaldi, Schubert et al. and I never suspected the ISR data of all being a big clamorous hoax.
Of course, because ther are hoaxsters and drunkards and various aspects of human nature, the scientific community justly takes the reputation of whoever is making a report into account. We trust that archeologists and paleontologists have scrupulously noted down the placement of things, info which the very excavation otherwise destroys but is important in piecing things together. The material objects remain available to examination by all but some things are observed only on the spot and you don't just find them in your backyard whenever you're in the mood for it.
In a talk, included at the beginning of C&R, a entitled On the Sources of Knowledge and Ignorance
Popper touches on these aspects, though I think he mainly gaves history as an exception, saying that for the rest reproducibility is more important than assessment of reliability. Even here he is aiming at stressing the importance of conjectures being falsifiable and this is the main line which pervades that collection of his works; after L. Sc. D. he seems to have become increasingly convinced of it being the actual solution to the demarcation problem.