I think a lot of Indiana cops don't actually know the laws. My friend had a bike without mirrors on it, and called the local police to see if it was legal, since it was an old bike. They didn't know what model year that motorcycles were required mirrors and referred him to the sheriffs office. Nobody at the sheriffs office could tell him for sure so he was referred to the ISP. Nobody knew at the local post, and they referred him to the Indianapolis post. He talked to 3 different people there, and finally found out that all bikes made after 1955 were required to have mirrors.
I think most cops would rather write a warning, rather than a ticket for a law that they don't know for sure exists.
I got pulled over for speeding on the interstate by a State trooper and he asked why i didn't have mirrors. I told him its almost a 30 year old bike, and i wasn't sure if it ever had mirrors. He said "Oh, well i guess it's ok then."
I finally did put mirrors back on my bike though, it makes riding in groups a lot safer i think.