Imagine as of 2019 (just to avoid the coronavirus thing), every human vanishes (literally) except for one per country, chosen randomly. Assuming around ~200 countries, that means there are 200 human beings. Survivors are entirely aware of the situation (that there are 200 people, one in each country). Most importantly, society's systems are still functioning (there is electricity and etc, at least for as long as they can work unmanned, days or weeks). So quickness is key.
The end goal is to meet each other (so the race can be saved).
The question is: what method can be realistically be expected to be used so that the 200 people get in contact with each other and then meet in one place?
The word realistically is crucial. For instance, a related answer (see below) suggests amateur radio. Yet, most people are unaware of it, let alone how to use it. Therefore, the core of the answer must be about finding the common denominator in terms of knowledge and access for random individuals.
PD: I've discussed this with several people, each offering different approaches. I have my favourite one so far but it might be better to wait instead of sharing it outright (and perhaps introduce some bias to answers).
Notice there is a related question here. That one assumes thousands of people survive a plague and must meet. There are rotten bodies and many people in the same city, so they can meet and start organizing. My question is way more extreme.
Two of the most voted answers for instance state:
Go to Times Square (because it is most likely possible anyone else will have the same idea) And keep here a sign noting in which direction you left Leave city And find closest farm or self sustainable living
That assumes that the direction indicated before leaving was successful in finding a place to live. Second, it assumes the Canadian or Mexican survivor will go looking for the US one, quite a biased perspective.
Another answer is amateur radio. But when one person only survives, it's very unlikely s/he will know how to use it or be aware of such thing.