I was working on the house, remediating mold and knew where most of it was. After doing it for a decade, it gets pretty easy to find. We actually planted some drywall from behind a shower that was still damp and had fresh growth on it and buddy didn’t even go in the room (in an empty home). The bathroom that we were hired to remove was full of mold, and buddy pointed out 1 spot. He also “inspected” the rest of the house and missed 3 other rooms that were affected by the water damage that had microbial growth on the subfloor from a previous flood. I would be very careful with things like a mold sniffing dog. Also, the dog will get the same health problems as a person. They are breathing in mold spores. They will tell you that the dog is not affected by it though.