Sometimes, even experienced people make assumptions and occasionally miss things. I know if I'm having an off day I can miss little things. FWs are funny in the way that they hold a needle and thread. It's counter intuitive and different from some other machines.
We spent several pages in the vintage area a year or so back trying to figure out why a Singer 201 was skipping a couple of stitches here and there. I even went through how to check timing with the original poster. Yup, it was a needle in backwards. I went in assuming that had already been checked. It's very possible that's what your friend did too. If it were me, I'd want to know what it was.