Isn't it amazing how such a small thing renders the entire machine "useless"?
When I was 19 I moved out and excitedly bought my very first machine of my own (basic 1994 Kenmore), I got it home and it would NOT sew. It broke thread immediately. I took it in to return or exchange it...turns out I was threading the needle the wrong way. D'oh! I was SO frustrated and upset at this "junk" machine and it was just operator error all along. I was so embarrassed to make such a rookie mistake, but lesson learned - double check the simple stuff that you're "sure" is right! (I still have that machine, by the way, and she still sews great despite neglect and many newbie sewing experiments.)
If I were your friend, I'd want to know what the solution was. It's not a bad reminder as obviously even experienced people forget to check the simple stuff, and personally I'd be a bit embarrassed to have missed it but I'd also find it pretty darn funny that it was something so simple after all.