[This happened on an Official server]
I wanted to reload my KA-M Drum mag, held the Reload button like usually to swap to my secondary mag, being a 30rd mag, and when i looked for the drum mag in my inventory i couldnt find it anywhere.

I have searched the area if it for some reason dropped on the floor, and I did a thorough search, checking with the vicinity tab, looking at the floor everywhere and then also went a distance away to see without the grass obstructing my view.

I was not able to find it anywhere.
I also did not have any inventory containers like a pot or protective case, and I also checked if any of my clothing items were collapsed. But none of this was the case,
the Drum mag simply vanished with all my remaining rounds

(me reloading the kam and then looking for the magazine)

(my last attempt of looking for the mag by scanning the floor from further away)