Well lets see.
First, the emotional stress/trauma of losing the item. As spelled out you do take a minor penalty on using any similar item for anything over the next six months
And yes, I WOULD make a player roll play that.
Second, it still means keeping the weapon with him no matter what, well past the point of rationality. It means a refusal to upgrade and a refusal to use the best tool for the job at every chance. You are still lugging the item around, babying it, scared of losing it. Doing irrational things to get it back.
for a -5 quality.
Again, I have issues like this in real life. I've lost items I've been attached to before and done some damn unreasonable things to try and fix it. You're not going to refuse to use your sidearm if your main gun runs dry, but you're going to do something stupid to get it back if it is lost. Something a good GM can play with.
And if you lose it, it should hurt.
The Hat from the Indiana Jones movies is a light example but a good one. Reaching his arm under a closing stone door to grab a hat. Stupid, irrational, dangerous literally to life and limb. But the memories meant that much.
THAT is the bigger part of the quality, and frankly for -5 that's a huge bit of baggage and role play to push in.