HELP for Crusaders of Might & Magic: Lost Mica's Key and can't return to Citadel

Hi everyone, I ran into a major issue and I'm wondering if my save is soft-locked.

Here is the situation: After I reached Corantha, I sold Mica's Key (since I had already used it in the Catacombs). I then completed all the Dwarf quests and obtained the Horn of Shattering.

Now, I am trying to return to the Citadel, but I am blocked by a locked door in the final passage of the Catacombs. I believe this is the same door that required Mica's Key originally. Since I don't have the key anymore, I can't open it.

I tried returning to the shop in Corantha to buy the key back, but the shop inventory has completely reset (actually, the whole Corantha was reset, too), so the key is GONE.

Is there any way to proceed? Is there a workaround or a cheat to get through the door? Or is my game completely stuck?

Thanks in advance for any help!