I find that explanation just a tad odd:

1) if the jet went on fire and the pilot grabbed that extinguisher to try to use it, surely the extinguisher would by lying somewhere near the aircraft, where it was discarded rather than being put neatly back under a bench several feet away.

2) if the extinguisher was PREVIOUSLY found to be inoperative, why was a new start subsequently done in the full knowledge that the only available extinguisher was useless ?

Sorry, but for me this does not seem to add up.

Gordon