My question involves a traffic ticket from the state of: Texas

I was on my way to work and one of my employees called me with an urgent issue on my cell phone in my car and I was not thinking and drove through a school zone while still on the cell phone. A police car came after me and had both visual and audibles going to get me to stop. I started driving in the shoulder lane immediately with the intention of stopping but realized I was close (around .1 mile) to my office so I drove down the shoulder to pull into my office parking lot (on the same side - on the right) since I thought it would be safer. The police officer of course cited me for using my cell phone in a school zone (guilty!) but also charged me with failure to yield to emergency vehicle.

I'm just wondering if I have a case to have the failure to yield ticket dismissed - I had no idea that would be a violation - I was just doing what I thought would be safer overall and had no intention of breaking the law. In reading the law it seems that this was more intented for the situation where an emergency vehicle was on the way to an "emergency" and needed safe passage so I did not realize it applied to my situation.