[gionnyct]

As mentioned, the never arrived or empty box method will suffice.

In terms of the latter (empty box), what's the size and weight of the drone?

the GLS tracking give me these box values:
Weight: 2.0 kg Volume: 3.0

why?

One thing.
Typically, all shipping businesses will periodically weigh their packages.
If you say that the package is empty, and UPS/USPS/FedEx (or anything else) say that they weighed the package and it weighed at its expected, it will be much harder for you to make a case. Also, if you were to say that the box was in pristine condition, you would have even a harder time making an argument
I would personally go with the never arrived method

in fact, my fear is just that, for this reason I want use the wrong item method
If I say that the package has not arrived, we will want to police report, because in Italy we must sign when the delivery arrives