Not usually. Two-sentence horror stories are often the product of creative imagination, designed to shock and thrill in a short span. But sometimes, they might draw inspiration from common fears or urban legends.
In many cases, two-sentence horror stories are pure imagination. They're crafted to evoke a sense of terror using creative and sometimes fantastical elements, not real-life happenings.
Another really scary one could be 'My phone rang at 3 am. The caller ID said it was me.' It plays on the idea of the self being something other or unknown, and calls at that time are always spooky.
I think 'The clock stopped at midnight. Then I heard footsteps.' is quite scary. It gives this feeling of something ominous starting right at a spooky time.
True two - sentence horror stories are terrifying because they can create a sense of unease in just a few words. For instance, 'The phone rang at 3 am. No one was on the other end.' It's the simplicity combined with the unexpected that gets to you. It's like a quick jolt to your nerves, and you start imagining all sorts of horrible things that could be connected to that simple event.