My trailers are all covered through the vehicle towing's insurance. Anything not picked up in that claim either diverts to my home owners (my RV) or my business insurance (my enclosed trailer).
May want to check with your auto insurance carrier on that. My insurance agent told me when these trailers are parked unattached from the tow vehicle, that's when they fall under the home owner or business insurance and are free from the vehicle.
Hope that helps. It made sense in my head explaining it. lol!
Cooking for the love of it.