You are correct!
I was thinking in terms of a dog being used to search public areas, such as starting outside the victim's home. The family has no more right to refuse such a search than they have the right to demand the airport K9 be taken away. You're correct that the family does not have to give consent for a dog to start inside of the house and they don't have to turn over a scent item.
Of course, in my theory of what happened to Bob, a scent item would not be needed. The use of an HRD dog around the outside doors of the house is what would have yielded results at the time.
Tangential and not at all related: when I was flying with my service dog, he was attacked by an airport bomb dog who had a clueless handler. My dog was jumped from behind, there was no doubt about which dog was at fault. The really stupid thing was that the handler tried to blame my dog and was just about lynched by the mob of eyewitnesses! Really, if he hadn't backed down right quick, I think he would have been hurting.
Travelling with my service dog was like being entourage for a rock star. More people knew my dog's name than knew mine and it was pretty routine for people I had never met to say "isn't that <name of dog>? Would you mind if I petted him?" After 9/11, while the National Guard was in the airports, they were enchanted with him when I explained he was the long coated cousin of a Belgian Malinois. They were young, bored people and they loved to make a fuss over him. It was always kinda funny to see these heavily armed guys (and a few women) bending over him, giving him scritches in all his favourite spots and baby talking him.
I was flying 3 times a month in that year after 9/11 and got to know a lot of the National Guard people pretty well. It was downright surprising how many of them discovered it was time for their break as I was coming up through security with my dog. They'd go with me down to my gate and sit to pet my dog and talk to me for awhile... and then sadly drag themselves back to the security gate for more boring.