According to canon, Melkor was able to carry away all the jewels of Formenos clutched in his left hand. He must have really big hands...
The detail that he was hoping to find Fëanor at home (and kill him, in revenge for the earlier insult when Fëanor slammed the door in his face) is from the expanded story in HoME.
Part 194: Melkor only knocks once
Next time: Part 195: Scene of the crime
Chibis by tektek.org