Alright there mate.
I think you might be getting a little confused to what Sparkystav is saying.
Depending on what year your IS is, your heated wing mirrors will either be on all the time, or switched on with your rear heated window.
Have a look at you’re A/C controls.
Which control unit does yours look like ?
If you have the top one, then you heated mirrors are on all the time, and can’t be turned off.
If you have the second one, then your heated mirrors will only work when you press the demister/heated mirror button.
The little orange light will always be on. Don’t worry about this, as it only comes on when you have the fans or A/c running, and can’t be turned off either (unless the unit is faulty).
Your heated seats have nothing to do with the heated mirrors or windows. They are on separate switches.
Also, when you say you have a missing “Jet Nozzel Cover”, are you talking about the head lamp washer, or the windshield washer?
If you are talking about the headlamp washer, I might have a cover in colour for you, but I will need to double check.