So I've lost Macready and I can't find him anywhere. I completed his companion quest to the stage where it says "continue traveling with Macready", so if anyone knows where he might have went, that would be nice. Here's my Idea for a future update; Bethesda should update the game so you can locate your companions on the map. It would eliminate the issue everyone is having with losing their followers. (Xbox player here, can't use console commands, before anyone gets wise.)

Check where you found him at, somethings they revert back to their OG spawns. Otherwise I'd say check the settlements you might've sent him to, fast travel and use the ringy dingy dong bell that gathers all your settlers it'll rally your companions in that settlement too