After I did the requisite murder of Grelod the child-abuser and visited the Aretino boy in Windhelm, during the Companions questline, I received the Dark Brotherhood's "We Know" handprint note. During the battle of Gallows Rock, I deposited that note into one of the Silver Hand's bodies.
Some time after completing the Companion questline (along with the DB) I received a radiant quest to retrieve an amulet from Gallows Rock. While I was doing so, after the exterior area battle, I looted the bodies (gotta love the resale value of those silver swords), I came across...
You guessed it, the handprint note. o.O
Strange, to say the least, and just a little creepy. Some force must be at work to resurrect the Silver Hand, especially since I wiped them all out!

Makes me wonder if stuff you put into dead bodies truly vanishes from the game.