Do you have some examples?

Probably because sour would make your lips pucker? I think lemons would be more obvious.

What happens when it’s too late?

Which is?

https://www.businessinsider.com/selfie-after-plane-crash-2014-1

Earl Snell Memorial Park in Arlington on the Columbia. There was a bunch along the southern edge of the park.

How would someone get started doing this?

This would make a good community, post news stories and have other people try to predict conspiracy theories about them!