You're not lying to the police in this situation if you've ever done anything ever remotely related to work on the "faux" phone only. That is still considered the "whole truth" in that scenario and would be easy to defend. It's absolutely absurd we need to even think ahead like this, but cops are (mostly) dumb enforcement. They don't actually know the laws in-depth and in many cases do not abide by them - which is the root of labeling them as such. Beating a cop at the game they're playing is not hard, you just have to know every question they ask is loaded and for a reason.