I keep all my cars on my home policy in my home state (where I live and where my DL is issued), and registered in my home state - NC, in this case. My crashpad car is in my domicile in another state. As far as my insurance company is concerned, it is at home with the rest of my vehicles. If anything happens, I was on a road trip - let them try to prove otherwise!
The only hitch to this arrangement is if your home state requires a state inspection. NC does. I was able to solve this by calling NCDMV and telling them my car was "temporarily" (this is true) out of state. NC accepted a faxed inspection report from my domicile state (they have reciprocity with several other states that do safety and emissions inspections) and all was square.
I've talked to people that have handled the situation several different ways, and this seems to be the best method. I'd just tell my insurance company, "I drove my car to work." That's true, and it doesn't matter how long it was there. If I'm not using it, it is parked in the airport employee lot in my domicile - in other words, "at work".
Any attempt to prove insurance fraud here (especially since none is intended) would be exceedingly difficult.