My 'brush with the law' in this regard happened some 4-5 years ago while on a mileage run on US Airways to retain UA status. I was transiting from one US flight to another at MIA and was trying to print my onward BP when I heard someone yell 'tackle him!' Then a fit man in handcuffs ran by within 6 feet of me, followed by a very unfit 2 men pursuing him at a distance. They were gone in no time, people around me didn't even bat an eyelid, and I got on my flight back north, wondering how often, like the OP, such transfers occur.