You are a normie on 2019 Earth and suddenly you can't find anybody. You've searched for a few hours, tried spamming out emails, random phone calls - no response. What would be the most jarring evidence that everyone in the world has disappeared?
You would be looking for assurance that you are alone, I imagine. By "most" I will settle for the largest number of people by some proxy like land area.
I imagine things like: 1) Within a few days it would be "dog eat dog" as wandering pets try to adjust to lack of pet food. 2) Within a week it would be "Lord of the Flies" as insects make food stores impossible to enter. 3) Within a few weeks it would be "trial by fire" as the stores of flammable material eventually ignite.
But I'm struggling to build the world of the first few hours, the first few months, the first few years, etc.