The phrase "single scrap" means not even a tiny piece or amount of something. It refers to having absolutely none or zero of that thing. Full definition
He was purely speculating — had not one single scrap of evidence that anyone was trying to commit fraud, which is EXACTLY what he was implying. (goodereader.com)
One of the challenges and thrills of drawing directly from life is to see how the white paper becomes street, or building or sky by the use of an adjacent single scrap of colour, a mark or a line. (thebricklanegallery.com)
and they are all ancient myths, invented my primitive men... and here we are in the 21st century without a single scrap of proff of any deity, demon, or heaven or hell, and so many still believe the BS (religion.blogs.cnn.com)