I'm the first to give people shit when obvious stupid stuff happens, but leaving your car on is normal in lots of places. My dad never locks his car and laughs at me when I lock my apartment when I simply go and get mail.
In some places I lock my car, in others I don't. Not saying OP shouldn't have locked his car, but I can understand the mentality of "who the fuck is going to jack a car when I'm right here"
I've helped a friend who went through something like this recently, so I only know as far as we were able to research after he was found to be out of luck.
As a heads up, the other posters are correct (for the US at least). If you ever leave your car unlocked and it is stolen, US auto insurance will only
maybe cover it if you have Comprehensive coverage. That is only assuming you have one of the major providers that include that as part of their comprehensive coverage. Even then, it will count as a comprehensive claim and likely noticeably increase your rates, moreso than other comprehensive claims, and much more than a normal car theft claim.
House insurance in the US does not cover theft without forced entry. An ex having a key and wrecking all of your stuff will lead to most insurance claims being denied, and in some cases outright cancelled. A random opportunist that walks into your house and takes all of your stuff will likely just lead to your claim being rejected immediately upon report of no forced entry.
I cannot speak to non-US policies, but if you are a resident of the US, DO NOT leave your cars or homes unlocked.
Edit: Just to clarify: "Normal" or not for your area, doing so is very misguided at best, and self-neglectful at worst. It takes seconds to lock/unlock a door for you, and can add crucial minutes for someone trying to break in, plus ensures you can file your insurance claims. Do not leave it unlocked.
