> that is clearly not

For one, you can't know if that's true as the image could have been manipulated to appear as such. For example you wouldn't know if a kind of steganography has been used to hide image in an image and that neuralhash picked on a hidden image.

> but I don't understand how they can get it on someone's phone

There is many vectors. For example you can leave phone unattended and someone can snap a picture of an image or since a collision may look innocent to you, you would overlook it in an email etc...