I used the Burnished Steel key to open a door in the main hold (a door in the kitchen level but not the one leading to the throneroom) and this caused the key to disappear from my inventory. I can now no longer progress in Raedric Hold and all doors are locked requiring 8 mechanics to open. When talking to Nedmar he keeps mentioning the master key as if I had it. Is this a bug or feature? Would be kinda sad to have to restart the game 10 hours in. (  

Its a bug.  Supposed to be fixed in 1.03.

i had the same problem. i farmed exp wherever i could to raise mechanics and i opened it after leveling

Thanks for the responses. Will 1.0.3 fix it so I get the key back or just so that it does not disappear again in a new playthrough?

If I remember correctly, there is a passage in the eastern wall that can be opened with a hidden switch and leads into the throne room. Might be able to use this one until they fix the key... no idea how much mechanic skill is required to find the hidden switch though.

The key is still missing from my inventory.