
Trivia: When Rory is walking down the street wearing the Predator mask, there is a bright red/orange alien walking toward him. This is a nod to the original Predator costume that looked like a big bug, the red/orange color was used to film the stealth camouflage scenes. The bug suit was scrapped after a few test shots proved how silly it looked. Jean-Claude Van Damme was in the original costume, but he was let go when the costume was scrapped. (00:45:20)
Answer: Well, in the case of Predators, it was violent criminals, mercenaries and military being randomly kidnapped and dumped on an alien planet. From the perspective of humans, it would appear that the criminals and mercenaries had gone missing in a more mundane fashion or simply died. If the Predators were covert about it, the Predator researchers would not be suspicious at all. So it's entirely possible it's canon.