A high school kid committed suicide at his school after stealing a Glock 26 from a family friend while spending the night. The guns were locked up by those cheesy cable gun locks that are mandated by law in at least two states, and also inside of a soft sided case.
A determined adult (for all intents, a 17 year old is as competent and resourceful at defeating cable locks as any adult) can bypass these locks in just a few minutes, especially if he has stolen the gun and is trying to beat the lock in the privacy of his own home.
I have a gun safe. That safe is bolted to the floor. That safe has a switch on the inside that is connected to my home automation system. As soon as the safe is opened, it sends a text message to my phone and if I am not home, sets off the burglar alarm.
Every firearm in my home that is not under my physical control is unloaded and placed in the safe. Anyone who wants to gain access to one of my firearms will have to enter my house without setting off my alarm, and then force open the safe without setting off the alarm. This is as secure a system as I can imagine making, within reason.
Secure your firearms. Don’t let an unauthorized person gain access to them. Gun safes are cheap. A decent one costs less than $600. Why would you invest thousands in firearms, and not be willing to spend $600 to protect them from theft?