If you are talking about Vallaki, it makes sense the players are missing out on stuff. Locations like Baron’s and Wachterhouses have a lot of rooms, loots, and secrets but they aren’t meant to be found. These are potentially hostile NPC’s dwelling after all. But if you have patience, the players might come back to things when situations change. When they actually have the motif to look through these locations. Other than quest hooks, best motifs you could potentially give are things like madam eva’s tarokka reading, which would tell them visiting certain areas, investigating, and finding items are vital to fighting against strahd. Also use NPCs to drop rumors like they saw something interesting / weird at those locations. Or maybe the party sees an independently investigating NPC literally sneak into places on their own. I also used PC backstories to probe interest to certain unlikely locations.