In Fallout 4 - It often happens just when we most need to address missions (or obtain new and valuable weapons that your companion disappears or he is not located in the place where you have sent him.
Some comrades are particularly stubborn and if you choose to send them to other locations will return to their home or the place where you found them or where they live normally. It happens often with Dogmeat that goes back to the Red Rocket Sanctuary station or Piper who goes to Diamond City in his newspaper. So if you can not find the companions in the place where you have sent them look their original locations.
Find your lost Dogmeat companion in Fallout 4
The Dogmeat tends to get lost often bringing the player to a long-standing and frustrating search. In reality this is not so because Dogmeat is to be found in specific strategic points of the place or where there are kennels, often behind many homes of the game. If you have sent him to Sanctuary, for example, there are 4 kennels to look for, located in the back yards of some houses. Dogmeat also does not respond to the call of the bell every time so you'll have to find him in various kennels in the place where you have sent him.
1. Send him in a small settlement. Tenpines Bluff is again the perfect example, and in this way you will have far fewer places to look.
2. If you want to send your dog to Sanctuary, for example, entered the construction menu and delete all kennels present constructing one in front of home, where there are also various workbenches and repair station for Atomic armor. This way you will have to stick to the mutt force in the kennel and you manage to find him in a few minutes as soon as you arrive at Sanctuary.
It seems that some disappearances can be attributed to annoying bug in the handling of the companions; hope that Bethesda will solve this issue quickly.