Solution 1:

Imagine you have a collection of objects including a sword, one day you can't see the sword and you don't know where it's gone, then you can say "The sword is missing", meaning it's absent.

Now imagine you had a sword and you gave it to someone, or you got rid of it, the point being you know where it's gone and you don't have it. You see a snake in your lounge and you wish you had your sword to cut its head, you miss the sword and you think "the sword is missed" (passive).