The light may not be a current issue, but without it, you're only guessing as to what caused it to come on.
If the light is now off, do we care what put it on? 

We don't, but the owner of the car should be interested...
I can see the next thread... "EML light is on again. What could it be?" or words to that effect 
To satisfy just you, the light was on because of plug number 4 mis-firing, and staying on when I drove two miles home. I replaced the Dis Pack and so got all cylinders firing. The light didn’t clear straight away, but left overnight the check system settled down so when I fired the engine up again, all was well. Simples.
I have been doing car mechanics, and now reading the OOF guides for decades, so am not a complete novice. I was worried yesterday when the light would not go off, got reassurances on here that it could be very temporary, which it was thank goodness.

I am sure I will encounter more challenges with this now 18.5 year old car, as I have in the past, but I now do not lose sleep over a bloody car. If the light comes back on, so be it. I will deal with it as I do with all challenges.
One of my daughters sons is partnered with a young women who last week gave birth to a baby by ‘C’ section under emergency conditions at St. Thomas Hospital London, warned that the baby, a grand daughter for me, could not live long, and so it died 6 days later. That for me at the moment is far more important than any fxcking car :'(