The argument of whether it exists or not is not logical.
If astronomers have not observed the planet that is going to be the problem does that mean it doesn't exist?
Just because you can't see something doesn't mean that it does not exist. It may only mean that you yourself have not observed it.
Hercolubus is real enough. The problem is that they haven't seen it yet. They are looking at a star system that they call Barnard Star. They consider it a red dwarf. They have spotted planet Barnard A, Barnard B, Barnard C and Barnard D. But that's not all of them. The one they need to be looking for is Barnard I. It's extremely large compared to anything in our 13 planet star system. It is 6.66 times the size of Jupiter. Funny how that ties into the Bible as an evil number but I think it is just coincidence.
Also note that the planet Barnard I is a lot further from it's solar center than what is currently being speculated. The scientists of this planet think that there are only six planets in the system.
If you would like to look this information up for yourself you will need to search for Star System Tylos and Barnard I not Star System Tyler like most people think. Tyler is simply a planet in the Tylos star system.