AI training is a one-way operation - you can't reconstruct the dataset from a model/lora/ti. Unless it's something really blatant like real people, widely recognised copyrighted characters like Batman or Iron Man - it's going to be hard to prove that someone used your art to train an AI model. I'm not required to publish my model or the datasets that I used anywhere.
It's about actually being able to use that content legally (and commercially) that matters to most in this conversation.