There Are Other Things Too.

The unicorn origami from gaff is simply just a coincidence, and this is what gets the smirk outta deckard at the end. It can be assumed that deckard has never told anyone about this dream and that it would be a very strange coincidence for gaff to leave him a unicorn just because it was the animal of the day. Also, don't forget gaff is simply another blade runner like deckard.

After Recalling Gaff's Enigmatic Final Words, Deckard Left.

Early in the film, deckard dreams of a unicorn during a drunken reverie. In the end, therefore, by letting them escape, gaff does them a favor. The unicorn didn't actually appear in the original theatrical release of the movie;

In Both Films, Seconds Before Rick And Rachael Step Into The Elevator, Deckard Spots A Tiny Origami Unicorn Outside His Apartment.

The unicorn are 100% original and designed based on images seen in the original blade runner movie. They’re amazing and look just like the one in the film! Origami unicorn, inspired by blade runner and gaff's origami, 3d printed unicorn, unicorn model, satire.

Isolation Player On Reddit Noticed That Someone Had Slipped In A Cheeky Little Blade Runner Reference:

In the director's cut and the final cut, there is a sequence in which deckard daydreams about a unicorn; A calling card if you will, letting deckard know that he was there and was aware that the nexus 6 replicant rachel was there too. Origami unicorn designed and sold by liis roden minimalistic origami unicorn.

The Origami Unicorn Is Gaff’s Final Prodding Deckard Suggesting That Deckard Has Found A Unicorn.

The final unicorn origami means that gaff has been to deckard’s apartment and has known about deckard sheltering rachael. The origami unicorn was left for deckard to find by gaff. For example, earlier in the film, gaff whipped up a paper chicken to imply deckard was a coward.