Several years ago I burned and blackened a couple of Stainless Steel
Pots and a Corningwear Coffee Percolator......for the same reasons
that your friend did.....The first time it happened I tried everything
like many of the suggestions mentioned here and to no avail. Then a
buddy of mine who was a High School Tech teacher suggested that I
soak the Pot for 24 hours or even 48 hours if necessary with Javex
(Javel water)........which is a brand name for a bleaching agent. The
burned blackened surfaces of the coffee percolator started to break up
after 24 hours and you could start to see white.....by the next day I
was able to clean what was left of the black stuff with less abrasive
but coarse scrubbing pads....if you're doing the scrubbing with Javex
still in the pot..wear something over your eyes and wear thick rubber
gloves......the pot was eventually as good as it was before my
accident happened. I used the Javex straight or pure and did not
dilute it because my pots were real badly burned......

I haven't had to do that in recent times because I am a lot more
vigilent about cooking times and avoid or try to avoid things that
would distract me and cause me to forget the action on the stove or in
the oven.

Good luck !

TJ