The only scriptural issue for a post-trib ONLY, is that the bible CLEARLY states when Jesus will return, which is when Jerusalem is surrounded by the armies of the nations of the world. That would be a very obvious sign.

Jesus said several times that we know not the day/hour/time when he would return, and he also told of people disappearing from their work, beds, etc. So there were foolish believers and wise believers, because they knew not when he would come.

And if you consider that Satan has been prepping the world to believe in aliens since, well, actually long before the 50's Roswell incident, (see artist's paintings with "ufos" in them), he will have a perfect lie to explain to the world and a war to go with it. Alientology will be the new world religion. Demons will manifest and probably convince everyone they're friendly.. This is real life, man! Crazy! It's going to happen!