Owner keeps it until it's needed then...
I'm not a fan, but if you're going to report a gun stolen then they'll have all your pertinent information already, the casing is to help track if the gun get's used in a crime, or turns up some other way.
I think it's prudent and responsible to notify the cops when a gun is stolen, and necessary if your gun is covered by insurance.
Giving them some spent brass may allow them to correlate that specific gun with a crime scene at some later time. So what? You already told them someone else is in possession of it.
If they match the brass to brass from a cold case file and they estimate the date of the crime as having occurred when you still owned the gun, you got some 'splainin' to do if their calculations are wrong.
People - including thieves and receivers of stolen property - commit crimes. Not the guns.
If the gun turns up, unless it's utterly wrecked, they can read the serial number and file it on hotgunz.com or work using the data they already have access to. If the serial numbers are wrecked, does anyone seriously believe some plod is going to start a hunt for a needle in a haystack to reunite someone with their precious hand-stippled Glock 19?
And would you even want it back?
