Is there any way to find a lost companion?

I had Piper with me, during the radio person hostage quest. Took Strong, as a companion on sight and sent Piper back to Red Rocket. She is not there. Traveled to other places and went back to Rocket, she is not there.

I know I can construct a bell, that will call but will it summon those not in my settlement?

Anyone help?

I think you need to head to diamond city. She sometimes heads back depending on which quest you have triggered.

I have the same issue as you with dogmeat, who I sent back to Red Rocket from Fort (Hagen?). However once when I switched Strog for Valentine I found out that they walk back to the location rather than just teleporting. It is likely our companions are simply in transit to where we sent them and will arrive after the journey is over

you can try and wait but it didnt work for me

i have the same problem and its not the quests because i have alrdy done the relevant ones for piper