Is it against the law / courier service policy to allow anyone to sign for the package?

I've lost my package at the moment and their proof of delivery is sign by an unknown person at a random time.

Bought item from lazada, pending investigation and the courier is NinjaVan. They provide the "proof" that was sign by anyone but me.

If worst come to worst, they are not taking responsibility, is it possible to lodge a complain to tribunal and win?

Any legal expert, please advice sad.gif