Miss. Pie, the bomb sniffing dogs alerted because that's what the authorities wanted them to do. When denied permission to search the car, they had to have an excuse, so they call the dogs. The dogs will "alert" on any damn thing the handler tells them to alert on. It's BS - purely a way to say they had probable cause to search the car.
If they ever want to search your bags or your car or your house or your person, they will get the dogs, and they will indicate that you have whatever contraband is necessary to permit a more thorough search.
Just keep this in mind - watch for all the news stories you see where a dog alerted for the presence of explosives and there is nothing there. They have close to 100% false-positive failure rate.
Gee, maybe they should hire me. I have had 100% success with my reports of (15 or so) natural gas leaks. Maybe I can be retrained for a new career : )
If they ever want to search your bags or your car or your house or your person, they will get the dogs, and they will indicate that you have whatever contraband is necessary to permit a more thorough search.
I have believed this for many years.
I don't doubt that that happens sometimes, but explain why they then went on to blow up a backpack.