If you're already unconscious from the SN making you hypoxic, then it's in your blood stream. If it's in your blood stream to that extent then vomiting will make no difference. It gets into your blood stream through your lower intestine, not your stomach, and AE's are no guarantee of not vomiting, many people who take them do vomit, many people who do not take them vomit, vomiting is no way related to failing in ctb.
The lethal (max) dose is 100 milligrams per kg of weight (it can be as low as something like 75 milligrams/kg) , so if you weigh 80kg then the lethal dose is 8gms (max) (could be lower than that). The standard stat dose is 25 gms, so that's more than 3 times the required amount. So if you "only" absorbed 1/3rd and vomited the rest out (unlikely) then it's still a lethal dose.
Most people start to feel nauseous after 5 mins, if you've kept it down that long then it's probably going to be a ctb scenario.
In my humble opinion.