Once when I lost Dogmeat, he returned to the gas stations south of Sanctuary. But, another time he completely disappeared, and I could have sworn I sent him to Sanctuary.
First Check the Doghouses
If you are on the PS4 or Xbox One consoles then right now this is your only hope. Apparently, he can end up in dog houses. There are 3 or 4 dog houses in sanctuary. I thought I had found them all, but in the image below the green dot (aiming recticle) is pointing at the location of a doghouse that I did not know existed where I found Dogmeat. It is behind the yellow crafting house towards the bridge. I just never walked over there for some reason. When I did, I found Dogmeat. I suggest checking it out:
PC Users Have Another Way
We’ll need to use console commands.
You can bring up the console by clicking the Tilde (~) key on your keyboard. It is usually to the left of the 1 key and above Tab. This console has a wealth of power, but we just need a few things.
We need the ID of Dogmeat and a way to get him to you. This will work with other NPCs if they somehow get lost.
For a complete list of companions and their IDs check out our companion list with their in-game IDs. You can then use the process below to summon them back to you!
Recover a Lost Dogmeat or Other Companion
We have determined that the Dogmeat ID is 0001d162
Open up the Console by typing Tilde (~) Type ‘prid 0001d162’ Hit Return/Enter Type ‘moveto player’ Hit Return/Enter Hit Tilde (~) again to close the console Dogmeat will shoot to you like he is being magically summoned and be next to you! Travel the Commonwealth with your Dogmeat
Finding the ID or Base ID of other NPCs
People refer to this by different names, but base ID and ID are roughly equivalent. You may have to load a previous save where theNPC or object was still accessible. Then do the following:
Open up the Console with Tilde (~) Click on the NPC A string will appear like this (000d0e9b) indicating the ID, but NPCs will have extra info after them like this [ER].
The string inside the () is the ID. NPCs usually have brackets after them indicating a type of something similar - they may look like this (000d0e9b[ER]) with another bit in brackets after the ID. The ID is still just 000d0e9b.
If the NPC indicator brackets are not after the NPC, you have probably clicked the wrong thing. Keep clicking around until you get the NPC indicator.
You can now login to your broken save and follow the same steps as those above outlined for Dogmeat.