Charles was actively looking for Erik, and following the action seemed quite a good hunch when he discovered him in the thick of it. He meant to have out their discrepancies in continuity right then, for better or worse.

Erik, he projected, just as Erik was lifting a strange looking helmet onto his head.

And then he was gone. His mind was snuffed out like a candle, much the way Charles had perceived everyone before he'd got used to what little perception the nanites left him. But he knew he was at full power, now, and Erik's mind had gone totally silent once that helmet was on his head.

Which Charles supposed was the point, going by the look on Erik's face.