There's a tool doing the rounds called "Stable Attribution" which claims to be able to identify the images in the Stable Diffusion training set that were used to generate an image
It's extremely misleading. All it does is show you images in the Stable Diffusion training set that are visually similar. You can prove this to yourself by running it against a photo you have taken yourself.
I took this photo. It was not generated by AI at all.