Lucky you were handy and had an extinguisher, otherwise their camping trip might have been a lot more memorable for all the wrong reasons....
Just a word of warning on those little powder extinguishers to, It pays to turn them over / up side down from what ever way they travel and tap the sides of the cannister to loosen the chemicle inside every so often ... O'l mate of mine had to use his on an engine bay fire pulled the pin aimed and pulled the trigger, two to three whispy puffs of powder and that was it.. nearly all the powder was compacted into the bottom of the canister from traveling over a six month period ..