Yeah, that person sent you the head with the texture knowing so.
If the texture is stolen, the person who sold you the head will receive a infraction not you.
You can only take ownership of an art if you make a deal. Since there is no deal, then by all means, that texture is not yours.
If you are seen wearing such an art, you are eligible to be reported for texture theft.
But I've seen someone sell full 512 with a robot set on. And the price was way too high for just a full 512, so I assumed that it was a package deal and that he was selling the set also.
In that case, would it be legal to use the set?