Well said, but in fact they don't need even that. They'd just say they smelled "strong marijuana odor" (the proof it isn't happened now on you, and how exactly you're gonna prove they didn't smell that?) or that a confidential informant (local junkie) told them he have seen a person looking like you doing whatever they want to accuse you of.

Qualified immunity pretty much guarantees there's no punishment for any shenanigan as long as it can be plausibly presented to a judge as the police believing it's lawful (it doesn't need to be lawful, just belief is enough). The worst they risk is evidence being excluded - so no risk at all vs not searching.