It sounds like you're disagreeing with something I wrote, but I'm not sure what. If it's the "faster-than-light" travel, I put that in quotations to denote that it's not really faster than light - but, while we may not physically be moving faster than light, the end results is that we've traveled a distance faster than light could make the same journey.
Also, everything on our end is theoretical. But that doesn't mean that another civilization doesn't already have the technology to travel from one end of the galaxy (or universe) to the other in the blink of an eye.
There are too many accounts from credible sources for me to believe that another civilization hasn't already visited this planet.