I've recently seen both the Maze Runner 1 an Scorch Trials. In the latter Thomas and his friends Escape from the organization WCKD to seek out a group called the Right Arm, however I never heard the Right Arm mentioned by name in the first movie, nor do I recall adults at the place the immunes were taken to at the beginning of the second mention them before the kids flee them into the region called the Scorch.
Where did Thomas hear of the Right Arm? Did he know about it before he was memory-wiped and sent into the Maze?