Cue the Indiana Jones theme, time to raid the Temple of Death to steal the Black Heart, the necromongers are worshiping it, and keep raising the corpses of dead villagers to serve as their shock troops and terror weapons. Go to Comment
Plus it is magical, the rules of death are cheated by the magic armor regardless of the system you are in, have it do whatever fits your game. Give them real damage after -10 and let them die of unconscience pummeling (if people even do that) if that is your wish, or say the magic saves them, doesn't really matter in the scheme of things. Magic will do as magic does or as you desire. Go to Comment
If stolen, I assume that the beaten person would still be revived since the armor already did what it was suppose to, ie. convert it to subdual damage. So they would heal, albeit a little slower.
Give it to the enemy. Especially one that was difficult and has been causing them much problems. If they take the armor, fine, if not, then all the better. Either way, "Johnny's back." Great way to bring back your favorite villian. Convert whatever they are wearing to this. Ta da. Go to Comment
I like the conspiracy angle.
If anybody did find out about the armor and wanted to fake their own death....
Perhaps given as a gift to somebody who is then "assassinated" but really kidnapped.
Man in the Iron Mask type deal where somebody must be "murdered" to protect them from true murder. Go to Comment
Another real world thing. White tea. Can only be picked two days a year, the two days before the flowers blossom. Could be a similiar plant that...is the deadliest poison known, cure known diseases or psychosis, or a potent herb that just tastes awesome.