Retired school nurse / health visitor here.
I would agree with daftbag - note it, but don't make too much of it at the moment. As so many have said, this is a stressful time for all, and it is most likely to be the memory lapse they have suggested. Fluff - what would worry me is that going to the doctor may add to stress.
I don't dismiss suggestions about petit mal, diabetes etc. but if it is of any significance it will happen again, and having 2 episodes gives doctors much more information to work on. At his age, in current circumstances, he is unlikely to be alone in a dangerous situation (riding bike on busy road for example) so I would tend towards 'watch and wait'.
If it does happen again OR if there is any family history of such illnesses, I would go to the GP.
All of this is given with the usual caveats about on-line advice of course!
I’m finished my festival poncho