I've never filed a claim for a recreational vehicle, but I know my insurance company has an "agreed amount" as do most insurance companies. (Generally a stock replacement bike, plus any aftermarket parts) My single seat sand car doesn't have a vin, but it is insured against theft, liability insurance isn't available, as it is a race-vehicle only. Most golf carts don't have vins either, and they are insurable. You can insure practically anything. Wedding rings, for example.
When I had my banshee, the only reason it was insured against theft, was because it was included with the policy. I couldn't "opt out" with my particular insurance company. It was covered both under my liability policy, as well as my umbrella policy, if I were in injure myself, or someone else while riding.
My point in the other thread, was that filing a claim on a damage that costs less than your deductible... If it was stolen, definitely it'd be worth filing the claim since you have NOTHING. I wouldn't file a claim for a chain wack, was my point.