Welcome to Tnet.
Very nice 'handkerchief' bowl. It might well be Murano, but without a mark, a label, or a presentation box you'll never know unless you can find a match for the design by Googling. Even then, you'll need to weed out the eBay sellers claiming 'Murano' without anything to support the claim.
I was actually in Murano a few weeks ago. You're quire right that many pieces are not signed, and especially not where the signature might show through and 'spoil' the artistry of the piece. Often they just have a label, which many folks peel off, and/or have the artist/workshop details on the box or on a card or 'certificate' within the box. There are numerous other possibilities though.