wrongly accused

*Let me preface this with, I don't dislike the police. I admire the hard work they do and don't think it is an easy job for meatheads. I could not do their job.*

Monday morning I was pulled over in front of a school near the one I work at. The officer informed me this was because I was talking on my cell phone in a school zone. Here's the thing. I was not on my phone. I hadn't had a single call or text all day actually. He then told me I was a liar. I handed him my phone and told him that he could check the phone records. He said that was not necessary because he saw my hand at my ear. Then he proceeded to question me about the hanging basket or petunias in the back of my car. They were for a friend at work. Then he asked me about where I was going and what I did there. I told him and what I taught at the school. Now, I am so upset about being accused for doing something I did not do, being questioned for the messy back seat of my car and it's contents, and also he was not thrilled that I pulled 2 insurance cards out of the glove box (one expires in a week so I had the new one already in the car.) I am practically in tears, begging him to believe me and, it is not even 8am. Then he made more grumpy looks at me and gave me a warning.
I am a little confused, why would I get a warning for not talking on my cell phone? Are you too pompous to admit you were mistaken? (maybe I was scratching my head or singing in the car?)
And why did he care about the petunia basket in my back seat? Are petunias the new street drug?
Last, why would someone need to be so grumpy at 8am?