Several years ago my sister had a fire at her place. In addition to losing the barn and offices her husband lost all his guns.
He was lucky enough to be able to recover what was left of them from the rubble. The serial numbers, including make and model, were evident even with the stocks burned away.
They had not planned ahead. None of them had been documented.
I learned from their error. I now keep an inventory folder of all my firearms. I take a digital photo of each. Annotate the photo with the serial number, make and model, any add-ons like scopes, stocks, LASERs and other options. I keep a spreadsheet of the mags I have as well. Because I have a lot of them. And tools, and other gear. I print all this off and keep the prints in a binder. That binder is in my safe deposit box with other important papers.
--Insurance supplemental riders is another story.