I must have been skipping through the text too quickly when I was on the mission to find Kellog. But does Dogmeat disappear for good, or is he hidden somewhere in one of the settlements?

Damn I miss that dog =(. Got this annoying woman called Piper following me around!

He is probably back at Sanctuary. There are a couple dog houses behind the houses there. He should be in one of them. For me he was in the one behind the first house on the right after you cross the bridge.

Also, Piper is awesome!

He disappears on my all the time and he's always in Sanctuary.

He is a dog with a mind of his own. He must find me very boring since he keeps leaving so often.

I had Dogmeat disappear on me while doing that quest too, so I used the console hack to spawn him at my character only for him to run off to Fort Hagen and remain outside and couldn't be made to follow me no matter what I did. It resolved itself once I entered Fort Hagen and after finishing that location Dogmeat is back to normal.

I found mine back at the Red Rocket station where you first find him - also after the Fort Hagen mission.

Any other time, he has turned up at Sanctuary.

piper is annoying as hell. dogmeat by is the best because the lone wanderer perk work with him.