I looted an AKS-74U with a mag from an unlucky person who ran into me. Later, I found a can of black spraypaint. I knew I could spray the magazine black, so I removed it from the weapon and made it black. Success!

Then I dragged the mag onto the weapon which was still in my hands. The reload animation startet, during that I tried to hover the spraypaint over the weapon to see if I could spraypaint the whole AKS too, it gave me the option and stupid as I am, I clicked it instantly, while still being in the reload animation. The magazine was neither in my backpack nor in the weapon yet...

Now I have a black AKS-74U and no magazine, because it vanished in the process. I presume the painting generates a new object, and since the magazine wasn't attached yet, it didn't copy it, and the magazine was attached to the deleted standard coloured AKS once the animation was complete --> goodbye magazine :(