I constantly lose old companions. Sometimes when I cannot find them I leave the area and come back and look again and they are there. I think it may be a glitch with them sometimes not appearing... My advice is to send them to Red Rocket truck stop in future when not in use as it's the smallest one and easiest to search.
I've lost count of the times I have lost dogmeat lol. Another thing to remember is that (on Xbox One) if you select B when given a list of places to send them to, then they go back to where you first encountered them (which, of course, is Red Rocket for Dogmeat). Someone else pointed this out to me... I had accidentally sent him back there when I thought I had sent him to the beach settlement previously. Maybe that is what happened to you?
You should have been able to whistle for dog meat & he suddenly shows up as if by magic. I think it was red dead redemption where you whistle for your horse & he comes running.