Hi Josric,
You should have gotten three 3d and three 50p coins, as well as a key for Room 9 and a note indicating that the lock of the file cabinet in Room 9 is broken in the lock box.
Can you not look inside the lockbox anymore, maybe it is hidden somewhere in inventory or the gremlin ate it.
If the above doesn't work maybe - the usual dreaded step - go back to the saved game and redo it.
MaG