The truth? Coming from someone who's been pulled over plenty of times, and spent a night or two in a cell...
If the cop wants to search something, they can and will. They will figure out a loop hole later to make it okay. If they know the law well enough, they can do just about anything they want to.
Then again... maybe that's just Texas cops. Either way, I'd always stash it in the trunk, under the carpet, under the spare tire, in a first aid bag... Then, they'd really have to want it to find it.
Speaking purely rhetorically here, of course.
