Maybe someone can clarify the DC coverage policy?

Issue:
My Hertz rental car was broken into (window smashed in), and the GPS unit was ripped out (the Neverlost monitor - which of course does not work on its own...).

Issue:
I initiated a claim with DC and was told that the Hertz GPS unit is considered personal effects and not part of damage to the car - and thus subject to secondary coverage. The insurance guide is not entirely clear on this. Covered damages include:
- Physical damage and theft of the vehicle, not to exceed the limits outlined below.
– Secondary Personal Effects benefits covers damage or theft of such effects. You must first file under other applicable insurance (e.g., home or business), then we’ll cover whatever is not covered by your insurance.

Question:
What category falls the theft of a GPS unit under which is part of the car? Is it damage to the car (and thus covered under primary coverage), or personal effects (and thus covered under secondary coverage)?

Thanks.