In reply to highaltitudebarista:
I manage my wife's seizure clinic - it is very scary to see someone have a full-on tonic clonic seizure, which this sounds like, if you haven't seen one before.
As other posters and you have said, it's not rare. About 1% of the population have a seizure at some point and a one-off is generally not treated. The side effects of medications and the hassle of finding the right medication makes the treatment worse than the problem for a single event.
Not all seizures are epileptic either.
Precipitating factors can be any one or a combination of dehydration, lack of sleep, anxiety and stress. There may be chemical or physical triggers (whack on the head being one - it needn't be even vaguely close to the time of the seizure - hence the scan. And for epileptic seizures, there is sometimes a focal source which can be surgically removed (sounds scary but the outcome of surgery is often very good indeed).
Without a second seizure, don't worry about it - easier said than done! And for what it's worth, seizure treatment in the UK is pretty good. We tend to follow the NICE guidelines.
Boatloads of information here -
http://www.epilepsysociety.org.uk
Remember not all seizures are epilepsy, the majority are one-off (more common in kids than adults - children get dehydrated very easily) and some are a result of stress/anxiety.
Feel free to email me if you have questions