Missing Abby

Took Jock out front yesterday.  I was going to let him sniff around the front yard.  Well, I turned my back to check on Duncan and when I looked back, Jock was gone.  He was halfway down the cul-de-sac head up just looking.  He wouldn't come when I called him.  He was looking for Abby.  I had to go get him.  This is the first time that he has left the yard since he came to me in 2009.  I may have to get a small puppy for him.  He wants to play, but Duncan does not know how.  He found Abby's sweater and carried it to the couch and had it tucked under him.  I feel so sorry for him.  I know how he feels.