The above reply is correct; the Police icon should actually be titled Speed Trap vs Police, as once they've caught someone it should instead at that point correctly be Shoulder Hazard and not Police which everyone reports. Now if it's a moving car there's no way to report that since the location will be out of date.

For mobile speed traps be it a police car or a temp speed camera, then you report the police icon on the proper side of the road. That is the proper way to note items that are not there for weeks.
Example the portable cameras over by FedEx Field that are only set up a few hours a week on the beltway (inner or outer).