I have 5 Lince on the shelf. Four of them have a sticker on the lens, one does not. I have 3 Matrix (same mask, but larger "regular" size) and none of them have the sticker. Yes, there is a paper insert in each box; I don't know what you think might consist of "anything else" in the box.
Stickers fall off, or perhaps are removed when a customer tries it on.
I also know from past experience that Cressi is not 100% on minor aspects of masks and packaging. (missing or wrong label and barcode, mixed colors used during assembly on the accent pieces of some masks, different size hard boxes used for the same product...)
You bought a nice mask, enjoy it. (It does fit you well, right? The Lince is for a slightly smaller face.)