Dealing W/remaining Pet When Other Has Been Lost

Our dog broke free from her color while vet assistant was trying to walk her and get a urine sample to be teseted. Kit is a very anxious dog away from the home and particularly when she is taken to vet or kennel. We rescued her from a shelter.
Anyway, she was so upset yesterday, she manaaged to get out of her collar and ran across a 4 lane busy road.We have not seen her since 10:A.M. on 11/19. Needless to say my family is distraught. We have put signs up, cotacted vets and shelters, and I have drived around for 10hrs. since yesterday morn.
I addition to the emotional loss, Barkley, our other dog, who was inseparable w/Kit has become very despondent and very lethrgig. I know he has be teribly affected by the absence of his buddy.
My question to somedody. How do I help Barkley thru this time. We hold out hope that Kit will be returned to us but.....
I would welcome advice very much.
Thanks,
DE