Finding out the hosting provider *can* be easy, but sometimes it is impossible (cloudflare, etc). But even then looking up where the traffic goes is not that hard and writing them a simple email is also not that hard. Again, if they don't do what you think would be right, you *could* start a lawsuite with *them*.
Maybe they have done that and they both didn't comply, but why are they now fighting with a DNS resolver? This doesn't solve anything, anyone can still access that site, if they use another dns resolver or do the recursive resolving themselve.