Leave a Salisbury steak and 1 human bone under the bridge at Sanctuary, he will turn up maybe
Happened to me.
Until you talk to him in Sanctuary, he doesn't seem to respond to the bell.
But I found him there on two play throughs, just check the houses.
When he leaves the Hotel, make a hard save.
Wait 48 hrs in Sanctuary, then check the houses carefully.
No luck? Reload.
On one playthrough, I literally escorted him home.
He walks slow and is very squishy.
It took about 2 hrs real time and multiple reloads.
He's worth putting in a shop...try to find him.