Just because God doesn’t mention something doesn’t mean it doesn’t exist. Do you not believe that modern medicine exists because God didn’t reveal it in Scripture?
However, there is enough in the positives affirmed in the Bible to know extraterrestrials do not exist by virtue of them being contradictory to Scriptural truths.
One of the primary premises of the Bible is to explain how to be saved, not how to be cured of any disease otherwise the Bible would be a lot bigger than it is. LOL! I believe that if there were beings on some other planet somewhere in His universe, he would have mentioned it, at least in passing.
I love these discussions; I learn much about how people think.