Interesting detail, thanks for letting me now. I had a look at the AI packages of all three visitors (Gelephor, Gellius Terentius, Trenus Duronius) and at least in the base game (without UOP) none of them carry skooma nor are scripted to find it. So even though the game implies they are skooma addicts via dialogue & environmental storytelling, from a purely technical POV they are not addicts. Getting stuck outside the shack checks out, though I don't think faction membership is the reason for that — they simply don't have the key to the door.
> from a purely technical POV they are not addicts
Videos show them performing the silly skooma-drinking animation while standing there locked outside the den, so they must have some sort of flag somewhere, even without skooma in their inventory.
> though I don't think faction membership is the reason for that
The wiki claims that patching them to add faction membership fixes the locked-out bug, FWIW.
In any case, in conjunction with this bug we no longer need to assume that the addicts in the den are loaded and simulating at all times in order to make the murdered-skooma-dealer story plausible. It seems fair to assume that potions (including skooma) could once be consumed (per the demo video), and that a "consume skooma" package analogous to "eat" would have caused them to seek out skooma. It's true that shopkeepers have stored their shop inventories in hidden chests since at least Morrowind, but if we're charitable enough to assume that some "acquire from merchant" behavior was ever prototyped, then it's not hard to imagine some sort of hack was added to make it seem as though shop items were "in" a shopkeeper's inventory for the purpose of the AI's environmental search routine. Even if killing a shopkeeper did not literally make their shop inventory available from their corpse (for player balance reasons), that could still have caused the murder itself to happen.
