He is the only companion I have used but I have lost him somewhere, is there a way to track him down?

Platform?

PS4

Did you change companions and send him somewhere? Regardless, I would start by checking the dog houses in the back yards at Sanctuary.

Definitely didn't do that, what I have been known to do is to accidentally tell him to 'stay' when I have been talking to him.

Then all I can suggest is to back track (if your memory is better than mine), or go back through your hard saves.

This happened to me the other day. I sent him home to Sanctuary and couldn't find him again for a long time.

Later on, I was scrapping the junk in the river and the little sh*t was swimming in the river.

If you told him to "stay" he will eventually get bored and go back to the last place he "lived" (if you never sent him to another settlement, he should be at the Red Rocket). Or if you had sent him to someplace like Sanctuary, he'll be in one of the doghouses scattered around there.

Try waiting a day or two and look in those places.

He just showed up. I had moved on and been to a number of places which is why I couldn't remember where I had last seen him - I ended up in Vault 81, and as I am about to leave, there he is, sitting in the lift!

He was out looking for a mutant hound in heat.

on xbox even if I told him to stay, I just fast traveled and he was there with me. he does disappear on occasion

Whilst pedantic, I prefer to take any companion to their base location and drop then off there.

Asking them to make their own way back is usually fine, but for the rare occasions it isn't, it's not worth the hassle.

I do this especially for Hancock due to his dying bug.. lol

All the companions become serfs in my adhesive farm when they aren't traveling with me.

Honestly, worst case scenario:

If you absolutely CANNOT find a companion that you're sure you haven't dismissed, just go and find another companion, ask them to travel with you, and then you'll be prompted to send the companion you're replacing to any of your settlements. Or in the case of running a settlement-free playthrough, it will default to wherever you picked them up from.