Phalanx's body flattening down against the bed like a startled animal is what gets the creature to really wake up. That big arm swooping in to drag their new friend away definitely does the trick. They stay quiet and still, like they could maybe become invisible right there in the middle of the bed, having no idea that the effort is not exactly needed...

And the fact that there are mixed signals coming from the two men's words and voices and body-language does nothing to reassure Phalanx that they aren't actually in trouble. When the tall man (the giant man) says to get out of his bed, Phalanx starts to scoot slowly backward, toward the opposite edge of the mattress.

"Sorry... sorry..."