I have a slight problem. When I returned to the Deepscorn cave to check on my dark minion, I found he hadn't returned yet. This happened before, and usually walking to the trapdoor exit in the Cloister solves the problem. However, instead of the minion, my horse entered trough the trapdoor.

It's quite funny, but also rather annoying. The dark minion seems to have disappeared, and my horse is stuck in the dungeon - everywhere I go, cities or wilderness, I get the message that my horse is waiting for me at the city gates. I assume the game is coded to give that message whenever you are outside and your horse can't reach you.

I'll upload a picture if you want, there is not much to see besides a horse in a room where it can't get in.

Is it possible that one of the mods (OOO, ZA bankmod, and Midas Spells) or one of the other official plugins is causing this? Or did I break the code when I console-summoned the minion when he wouldn't return a few days ago? (Yes, I know I should have installed the unofficial patch instead of trying to solve it myself, but I was too lazy.)

Edit:
Forgot the most important question. What can I do about it?

I have not heard of this before in the unmodded game, so. . . .

Are you sure when you console command summoned your minion, you did not summon your horse (wrong Ref ID)?

Here is what I would try:
Get your horse's Ref ID up in the console by opening the console and clicking on your horse. Note the horse's Ref ID for future ues. Close console.
Step outsite your lair into the outdoors.
Open the console. Your horse's Ref ID should still be up in the console. If not, use PRID Ref ID to get the Ref ID displayed at the top of your screen.
With your horse's Ref ID selected, type moveto player. That should move your horse to your exterior location.

This works, thanks, but can I make sure it doesn't happen again? I guess I'll have to install the uop after all.
I did really summon the minion, after I did so, I told him to go find a new victim, and only a few (ingame) days after that my horse 'entered' the cave in his place, without me using the console.

Also, sorry for placing this wrong.

It occurs to me that, after fast-traveling, when "your horse is waiting for you outside the gates," you might have been able to just walk out to the stable and get your horse then.

Anyway, you seem to have fixed your problem.

No, it was not at the stables, I tried that. When I walked out of the city, I got the notificaion again and it was nowhere to be seen.

Sometimes Oblivion eats horses...when your horse doesn't appear at the city gates like it should after fast travel, IIRC they go back to the stable you bought them from. Have you tried checking there?

I did, but this problem was unrelated. I always got the 'waiting outside the city gates' message, even in its original stable. And whenever I went back to deepscorn, it was waiting for me inside.

Anyway, I solved it now, and it seems to be stable now. I needed an 'enable' of my dark minion and a 'disable' to send him away when he didn't want to leave, after that the script picked up again and enabled, disabled and teleported him where he should be.