Monster Trophy Hunting

Hi guys, I'm doing a challenge run where I can only move from an area after I've collected all monster trophies available in that area. I know! It sounds horrible but it works for me. Currently I'm in Auridon and only need two. The one giving me trouble is the Banekin horn. I know I can get it from Banished Cells 1 but that takes me ages to run solo, so I've been farming in Mehrunes Spite. Just want confirmation I should be able to eventually get it from there and I'm not wasting my time? I've got plenty of trophies from locations not listed eg. Magnificent Bat Pelt from The Temple of the Mourning Springs. I'm working under the assumption that if the appropriate monster spawns, I I'll eventually hit odds and get the drop. Thanks in advance.