My question involves criminal law for the state of: Missouri

Alright, a few days ago a friend and I went camping at a conservation area near the Missouri River. He had about a gram of marijuana and a one hitter pipe on him. It was about three in the morning when two conservation agents came by-in the sketchiest way possible. The literally snuck through the woods without any lights until they found where we were camping. Anyway, my friend was the first one to talk to them. I was quite a distance away fishing, while he had the weed and pipe on him next to to the fire. Since he had it on him where they could see, he admitted to having it. They had me come over and asked if I had smoked any of it and I, thinking honesty was the best policy, said that I had smoked a few hours ago. Then they took us both to their truck, searched both of our vehicles, and questioned us. My friend claimed both the pipe and marijuana and the marijuana was in a pill bottle with the friend's name on it, on his person. The agents also asked me to write a statement, only talking about the events of us smoking marijuana, which I did.(Thats where I feel like I screwed up.) They write him two tickets, talk to him for a minute, ask me for my information then write me a ticket also. I ask them why I'm getting a possession charge and they say it's possession by consumption. This is my first time ever getting in trouble and my friend and I were completely compliant and cooperative to both of the conservationists. So my questions are...
1.) Why, exactly, did I get a possession charge?
2.) Can I get this dropped?
3.) How can I fight this?
4.) Anything else that may help me?