I recently purchased the Halo 5 edition xbox one console and when I hooked it up yesterday and went to download Halo 5: Guardians from the store, well there was no download code for the game in the box that the console came in.
Did you get a receipt or note with the box? It could be on there or maybe it was emailed out to you? Might be worth contacting the retailer you purchased it from and seeing if they can help you out