So, he then had 'probable cause' to rummage through my car...
IF ya gave permission for him to search your vehicle, you're da cause of da rummaging!
If he claimed probable cause, you request (first), then demand (second) a search warrant!
'They' (as in Napoleonic LEO personalities) will try to brow beat you with BS. Know your rights... too many have died to protect those rights for anyone to 'surrender' 'em!!!!
Just a lil' hint that may work in your favor... politely request to speak with the LEO's supervisor. It exposes the LEO's lack of knowledge and can highlight their ignorance/arrogance, which is an ego blaster for 'em (not counting da positive educational aspect)!
BTW, I respect LEOs and have no issues with da non-Napoleonic personalities! They all have a tuff job.