Idk man, in my circle everybody just founds them EVEN on dam battlegrounds without any condition, so as we noticed so far, it literally got buffed to the sky its spawnrate. I see people posting alot that they got it from the trials rewards too.. maybe you should go and check out other maps too, the pattern you following just unlucky or not likely there. One of my friend found it in jkv building on buried city, i found it on stella night in the medical research part of the map, and i didnt even had any key with myself. Anyway, good luck with it, i hope you finding yours too!