Insurance guy here. A trailer being covered just because it's hooked up to your vehicle doesn't necessarily mean you have coverage. In fact that is a very common misconception. Say I have a $15,000 gooseneck, they aren't going to cover that just because it's hooked to my truck. However, you may have "non owned trailer coverage" on either your auto or home policy, possibly your ATV policy. Since it was your friend's trailer, you may have some coverage there.
Also to the guy above me who says "I have always understood whatever your towing is covered by auto policy. If you can find your actual policy-the 20+ page one they mail you, it may have it in there". That is incorrect. The insurance company doesn't know if you've got a $1500 utility trailer or a $250,000 boat behind it. They are not going to pay for anything that isn't on it's own policy. Trust me on this one.
Now, OP, if you have your home, auto, or atv policy with the same common carrier, all 3 or just two, there may be a provision where if you have a claim that derives from the same loss, which you do, they may have a provision where you pay the highest of one deductible. Not all have this provision, but some do. I would ask if they do. Some company adjusters don't even realize this.
Also look to see if your homeowners policy has person property replacement cost. Many do. If so, start a list of what personal property got destroyed and figure out what all it would cost to replace each item, with tax.