I always wear pants or shorts with a zipper pocket, and I only bring three things with me to the park; keys, camera and phone. Although I don't have internet or texting on my phone, I still take it with me to the parks to see the time and to call other members of my family if we get separated. Having a phone with you is also a safety thing. A lot of parks including Great Adventure and Dorney have a number to contact park security if you need to.
Also, if operators check for loose articles when the train leaves the station, then they and the park are cleared if something happens. If someone decides to take something out of their pocket during the ride and it falls off, that would be that persons fault for not following the rules and they will have to suffer the consequences if someone gets hurt. The park enforced it by checking.
I think kicking someone out of the park for having out a loose article is too much. I don't want people breaking rules, but that seems harsh.