This "probable cause" bullshit is used all the time. The dog didn't do anything, but was just an excuse to abuse the guy's rights. It's "conviction by canine."
The way it should work is, if a search is made on phony probable cause, and then nothing is actually found, the cops get charged with a gross violation of rights. If that were the case, then they'd be much less willing to do illegal searches. As it is, once they conjure up some fake "probable cause," they can pretty much do whatever the hell they want, and there's nothing you can do about it.