I have never had an issue vaping in view of cops, then again I think they are looking for specific behaviors. For instance if you see a cop and suddenly try to hide your vape, get fidgety, or quit using it, they might get suspicious of why you are trying to hide what you are doing. I just ignore them or nod if they happen to make eye contact and go about my business and they leave me alone.
I never have, either, and I work in a field where am frequently in contact with the police and other officials. I think our local police force is much more aware of what vaping is and what signs to look for. If blowing clouds out of the window of my car was suspicious, I would have been pulled over a long time ago, lol!