I can't say it too often: Keep copies of your insurance policies, forever, in a place you can find them. If at the beginning of your policy year your insurer or agent sends you only the coverage selection (or "declarations") page -- the page that summarizes your coverages -- ask for a copy of the entire policy. Do it immediately or you may never get it. And when you get it, make sure that the policy forms and endorsements provided match the forms and endorsements listed on the coverage selection page.
In almost every insurance coverage dispute I have ever been involved with, whether on the side of the insurer or the insured, the first challenge is obtaining a copy, preferably certified, of the policy. Whichever side I'm representing, it generally takes months.
Don't just keep your most recent policy. Keep all of them. For decades. Forever. If you have an occurrence-based policy and get hit with a Superfund suit -- say a property you owned for five years in the early 1990's has been discovered to be a site of toxic waste -- there might or might not be coverage under policies issued for each year that you owned the property. If the policies differed from one year to another, even if issued by the same insurer, there may be coverage under one year but not others.
Chances are that if the policies were issued not too long ago the insurer can, eventually, provide or recreate a copy. But at some point old documentation, especially but not exclusively from before the advent of computers, is lost. Insureds have the burden of proving coverage under a policy. The easiest way to do that is to provide the court with a copy of the policy, not to guess, "When my grandfather owned the company he was friends with an adjuster at Acme Insurance, so . . ."