I believe this is a misunderstanding on your part. "Like lightning" does not mean that it is lightning. The most common occurrence of a light going across the skies is a comet and considering the cosmological signs in Mat. 24:29 a comet fits right in.
I believe people did miss it because they did not know what to look for or were not paying attention.
sorry but it's lightning, or like the flash/gleam of a lamp. it isn't something outside/apart from self.
lightning that flashes across the sky is called sheet lightning. it doesn't have contact with the earth. i've only ever seen it once in my own life.
lightning
Matthew 6:22
“The eye is the lamp of the body. If your eyes are healthy, your whole body will be full of light.