... told me it would take weeks for him to work it out of his system...
This doesn't sound believable to me.
A bit like the old 'Bruce Lee's body was so fit and pure that it was an aspirin that killed him'
... told me it would take weeks for him to work it out of his system...
It would generally be very small. There may be rare instances where breathalyser detectable levels of ethyl alcohol are generated by the body, so-called auto-brew syndrome, but these are very rare and studies (Japan and the US that I am aware of) indicate common traits amongst the individuals where this happens -i would imagine everyone has some small amount of alcohol in their system ...
i would imagine everyone has some small amount of alcohol in their system even teetotallers,fruit or veg will ferment in the stomach.