Evidence of reversal of the arrow of time.
Evidence of an effect occurring before its cause.
I'm not saying it's true, or that it will be discovered.
I'm just saying that if it is ever discovered, it will first be seen in some phenomenon that occurs at the level of interactions of subatomic particles and the forces that mediate their interactions.
I agree with you that if it ever happens, it will be in some obscure mathematical circumstance that only a physicist would understand. But I cannot fathom it ever manifesting in the “time travel” types of scenarios common in science fiction. It is simply not possible to unshatter a glass.