Theft of package contents: how can I get compensated?

Good evening, I sent 5 items in a package and upon arrival, there was only one item left (in its box). No matter how much I explained to Vinted that I wouldn’t have used a large box to put the small box in (as the free space was for the other 4), it’s blocked. I found a photo of the package’s interior, taken hastily, and it’s not enough (I didn’t include the tracking number and didn’t take a photo of the outside - or deleted it). All I can recover in value is the remaining item in the box, which has almost the same value as the return shipping costs. This is ridiculous. In this case, can the carrier accept my dispute and refund me for the incomplete package, please?

I’m not sure, but normally the carrier weighs the package at several points. This way, they can detect if the loss occurred during transit.

I heard about that and it certainly explains why the thief left an item