Since I finished Thieves Guild's Glenumbra story I (I really counted) farmed 48 treasure chests (maps and overland), 29 safeboxes, 16 thieves troves. Performed around 12-17 Glenumbra Thieves Guild daily quest and 7 heists.
I got the werewolf colors (Black is not black, btw), got the "Rogue Tomb House", got several less interesting gear motifs.
Found ZERO keys.
Some say "it's not open yet!" despite the tomes points already in place; others say "i got 20!". HOW can we get it is an obscure information. Several theories exist.
Well, either the Nowhere Key find chances are so, so, SO low that only people that bought a "VIP Nowhere ticket" can find it OR somehow they are so perfectly hidden that the game RNG probability data itself forgot where they are and deny us any possibility.
Either way, I honestly think that I (and so many other players) had spent a huge number of hours of my real life trying to find them so I deserve at least 5 FREE keys when ZOS get devs enough to give some updates and fixes in the unforeseeable future.
Honestly, ESO need better INFORMATION about a lot of stuff going on OR NOT going on.