I guess now you know different. Based on your description, it sounds like the officer wouldn't have even seen your gun had you not said anything. My advice would be to continue as you have been doing minus notifying the officer upon approach. If directly asked by an officer if you have a weapon, by all means inform. But only answer the question being asked i.e.As far as telling the officer that I had a weapon in the car, I feel like it is just common courtesy. Better to tell the cops up front and get it out of the way than get arrested when they freak about a gun that you didn't tell them about. I am sympathetic to the stresses involved with their line of work and try to look at it from their point of view.
"Do you have a weapon in the car"
"Yes"
"Where is it"
"In a box under the seat"
Unless you're one of those YouTube 2a "advocates" there's no reason to give a heartfelt soliloquy roadside.