Good to alert those who might have vasovagal syncope to the potential issues with dietary change. I haven't had vasovagal problems, but was interested in blood sodium levels on initiating a low sodium paleo diet and checked them from time to time. Just curious, do you have the results of any of your blood chemistries and in particular your blood sodium levels during the course of your problem and recovery?
Intracellular magnesium deficiencies are extremely common and often cannot be ascertained from blood Mg levels, which are very poor indicators of intracellular Mg status. Proper intracellular magnesium levels are essential to the operation of the sodium potassium pumps which operate in our cells, and an intracellular magnesium deficiency could cause retention of intracellular sodium through inefficient pump operation, which in turn could lower serum sodium levels and cause hyponatremia. Elsewhere in this forum, there are good posts on restoring a magnesium deficiency, the process of which is not necessarily simple or straightforward.
Dehydration is common during outdoor activities and can strongly predispose toward syncope. There is sometimes a tendency for primal folks to be more relaxed than others about hydration during such activities, but if one has a history of vasovagal syncope, maintaining hydration is probably very important. A good reminder on your part for anyone with this issue.