How Do I Make My Dog Pass A Foreign Object?

I went to the vet yesterday for routine shots for my puppy--that morning my son and husband said they believed he hasd eaten a sweatband that's worn on the wrist. The doctor said she thought he would pass it if he did swallow it. He's gone to the bathroom since then, spit a little food up a couple of times, but not passed it. How long does it take to pass? Should we promote going to the bathroom by giving the dog something?