If the POA authorized the transactions it doesn't matter.

If the banks had to wipe away debt from every gullible person there would be no reason to be careful, if there was even a .001% chance that a scam was real you may as well participate and hope because you have no risk.

The other factor is how long ago it was. Any evidence is long gone. I don't see you not being stuck with this unless you implicate your father.