Never travel by any form of transportation that requires bag inspections when carrying large amounts of cash. If you're driving, pray you don't get pulled over. Civil asset forfeiture is a real thing. The authorities can (and will) just say they believe your cash may be intended for criminal activities, confiscate it, then send you on your way without charges. Oh, and you never get your money back, period. Sure, you can sue, but unless the state is one that reimburses for attorney fees expect to get back 65% of your cash at best. This is not an isolated, rare situation and yes, it can happen to you.
It's important to note that in a criminal case, the burden of proof lies on the state--they have to prove the defendant's guilt. In a civil matter, the burden of proof lies on the plaintiff. If you're suing the state, they don't have to prove anything--you do. It's a difficult burden to meet, like proving to your insurance company that you'll never get into an accident.
Don't think police aren't aware of this, or its possibilities. One sheriff in California repeatedly did it to an armored car service, netting over $1 million ($712K in one stop!), and has so far gotten away with it. The video below details the case. You'll get the idea within the first 5-6 minutes, but 17 minutes are well worth watching just to see how preposterous the entire case is. In one case, they stopped the armored car for activating its turn signal too early.
If the attorney's name seems familiar, it's because Steve Lehto is a Mopar guy. He wrote dozens of articles for Mopar Action, Mopar Muscle, etc. over the years. He also wrote books on the Turbine Car and the Superbird/Daytona.