Yes, it is.
The thing to note is that you look for the most probably forms of communication based on the environment. If you have a hypothesis, you can test it, as in the cases provided in the video I posted. if it data doesn't fit, you move on to other possible channels.
Alternative means of communicating that we have no way of sensing or measuring would be indistinguishable from ESP or other psychic claims.
We can still find out if there is an undetected psychic communication simply by setting up the tests and systematically ruling out all the forms of communications that we can sense and measure.
At the end, you will know that you don't know something, and even that is valuable in science.
Edit: So on a scientific level, one could say that there is something that exists which we cannot explain or imagine right now, but it doesn't fit any of our current theories or observations.
All the best wishes,
Faysal
) but their excistense is a fact!
