You're right — in Combat Zone drops aren’t protected and can be picked up by anyone, and I get the logic about anonymous players and PvP over drops.
However, in my case, I was mining with two of my own characters, and there were absolutely no other players nearby. Still, the ore would disappear instantly the moment it appeared on the ground. That’s what makes me suspect it's a hack or bot being used to instantly collect the drops — possibly even with some kind of cloaking or invisibility script.
To add to that, as I mentioned above, I was attacked by a female ninja who would only appear during the fast attack animation and then vanish immediately after, both from the map and from sight. It’s not just standard stealth — it felt more like a total disappearance.
So something fishy is definitely going on here.