The police don't come up empty handed.
If nothing is there then it never happened. Down the memory hole it goes and it never happened.
If something is there, I get to hear about how the dog magically evolved the ability to smell pills.
You'd be incorrect. At my agency, it nothing is found, it's documented. It's the same way with all out handlers. I obviously can't speak for all agencies, but that's the way it works with us.
As far as using dogs, I've only done it a handful of times. There was once, where I thought I smelled something and the dog confirmed it, and another when I thought I smelled something, and the dog told me to check my sense of smell. I don't like the idea of "thinking" I "might" smell something, and doing a search. I want to know, and a dog is invaluable in that regard. You can trust that there are frequent times when a person "thinks" they smell something, go into a car, and are wrong. You can be upset with that, but it unfirtunately happens. But a dog put that notion to rest, rather than have an officer that honestly believes otherwise, searches.