I guess I got lucky.
A mate and I were having "A quiet smoke" at about 1:00am in my car, parked in a National park car park. Lo and behold, a patrol car pulled up and asked us what we were doing. My mate replied "Having a quiet smoke". He asked us what we had and we were honest and told him everything, even showed him our bong and how much weed we had left. He then asked for my licence, which i gave him and he took it back to his car to check it out. I had and have no criminal history or "flags" as they call it. He returned a short time later and handed me my licence, and proceeded to tell us to have a good night. He then turned and started to walk away. Halfway to his car, he turned back and said "Oh, and dont forget to get rid of that stuff". I honestly could not believe our luck. My mate has had other similar experiences with similar "cautioning" results. Maybe the paperwork was just too much effort, maybe they had a call to another "more important job". We'll never know. I have been careful since but consider myself quite lucky. We weren't arrogant or assholish, just open and honest. Maybe if we tried to hide something or talk our way out of it, it could have ended up differently. I think it just depends on the officer at the time.
Im not in USA by the way. Down under as they say.