Sorcerer First Nightmare Dungeon

Good morning.

Yesterday I had the following problem:

I was doing the first nightmare dungeon with the sorcerer (I was at the final boss) and the game disconnected me due to a server error.
When I logged back into the game, I no longer had the ‘Nightmare Sigil’ item, nor was the nightmare dungeon active. Therefore, I can’t reactivate it because the consumable was used up. I would appreciate it if you could help me.

Thank you.