I'm playing the PS4 when I got that glitch where a character goes missing, problem is I'm playing the PS4. To add further pain it was MacCready whose one of my fav companions (whose none to bad looking I was hoping to romance him) and I had recently activated his quest (but hadn't finished it).
Anybody have anything I can try to get him back?
PS: I think Bethesda should add something that summons a companion to you (similar to the bell but personalized for companions and reloads them to yer location - that might fix the issue).

(On a side note - the ability to name yer unnamed settlers would be cool too.)

Look at your quest logs, if you have a quest where he is to meet you somewhere that is where he will be. He will be waiting for you.

This has happened with Dogmeat, and The Detective with Piper to me when I couldn't find them in Sanctuary.

I am betting they are waiting some where for you.

If that is not it, did you do a lot of things he didnt like? Maybe he left because he didnt like you actions ? Not sure if that can happen in this game.

PS you do have the bell in your settlements right? When you ring it all the settlers in that fort will come to the bell.

I've tried these (yes I have the bell and rang it). I'll search the area of his quest again, but I didn't see him when I checked there before and the two of is got along fairly well.

Found him in a warehouse in Diamond City of all places! I only found him because finishing his quest requires talking to him so the map pointed me to him...